Though the judge initially cited how Conley needs psychiatric care, he sided with prosecutors in the end.
"What is it that will cause others to stop" in the future, Judge Raymond P. Moore said during sentencing.
Before sentencing, Conley wept as she read a statement saying, "It was after arrest that I learned the truth about the ISIS that I was taught to respect."
She talked about her ongoing journey into Islam.
"Since my incarceration I have had a chance to read the entire Quran," she said. She concluded that "the scholars" she had been following in her online research about Islam had distorted the Quran, she said.
"Even though I was committed to the idea of jihad, I didn't want to hurt anyone. It was all about defending Muslims," she said.
She called her situation a "life-altering" experience and said she now wants to be a "catalyst of good" going forward.
"I am deeply humbled by this opportunity to grow," she said.
"I do not believe I am a threat to society and I ask you to allow me to prove it," she pleaded to the judge.
Conley's mother waved to her with tears in her eyes as Conley was led out of the courtroom. Later her parents released a statement online criticizing the U.S. legal system for making an example of their daughter in trying to discourage others from turning to extremism. If "the government is willing to sacrifice the future of a 19-year-old American citizen to drive the point home ... then we feel the terrorists have won this particular battle in the war on terrorism."
Outside the courthouse after the proceeding, Conley's lawyer, Assistant Federal Defender Robert Pepin, told reporters he was disappointed with the sentence and noted that the plea agreement imposed limitations on any appeal, which the defense is considering.
"I think the judge gave a sentence he thought was appropriate. That's all I really have to say about the sentence," Pepin said.
He said he wanted Americans to know that his client is a wonderful person. "Her future will be bright. She will get past this," he said.
'Not taking any chances'
But Moore said Conley's plea agreement gave him limited options on sentencing.
Under the plea agreement, Conley faced "up to five years in federal prison and a fine up to $250,000 for conspiracy to provide material support to a designated foreign terrorist organization," federal prosecutors said.
She received credit for cooperating with federal authorities, according to the prosecutor and the judge.
Her prison sentence will be followed by three years of supervised release and 100 hours of community service, in which she has to interact with "ordinary people," Moore said.
He also prohibited her possession of any black powder or explosive materials.
"I'm not taking any chances," Moore said.
Conley's plea was made last year in exchange for a reduced charge with a lighter sentence.
During Friday's sentencing hearing, U.S. Attorney Greg Holloway said Conley has been cooperative and willingly provided information to investigators. He argued that a four-year sentence would send a message that the U.S. government uses restraint, but consequences are serious in terror cases.
Moore interrupted the prosecutor at one point saying, "That woman is in need of psychiatric help."
"I'm not saying that her decisions were all a product of mental illness. ... But she's a bit of a mess," Moore said.
The judge referenced Conley's psychiatric report that stated "she is not a terrorist."
The judge also alluded to a series of events from 2011 to her arrest in 2014.
"There is a history of events that would make for a bad movie," Moore said.
Conley almost agreed to marry three different people in a matter of months, according to Moore.
The prosecutor said Conley was "pathologically naive."
Added the judge: "She has no history in the criminal justice system. She is very young. ... Teenagers make dumb decisions a lot."
Conley looked relaxed in court. She smiled at times while talking with lawyers before the hearing. She wore a blue and white jail uniform, a head scarf and glasses.
Pepin said while Conley has been in jail, she has been studying Spanish and macroeconomics, writing letters to her mother, sisters, friends, even "Allah," talking about religion and her desire "to understand."
Her lawyer said she has gone through a complete transformation in the past nine months. Pepin argued that "the things that she believed at the time she was arrested she does not believe now."
He noted that Conley, a convert to Islam, changed her adopted Muslim name from Halima to Amatullah, because she is a different person now. Amatullah means female "servant of Allah." Conley initially took the name Halima after converting to Islam.
But Moore adamantly responded, "She had another name before Halima."
"Don't tell me that changing her name means she gets it. She changes her name like I change my socks," the judge told the defense.
'A string of defiance'
The judge said a belief, even if she was misled by ill-intentioned extremists asserting religion justifies violent jihad, does not excuse her actions.
"There is a string of defiance that rolls through her life that I have not seen change yet," Moore said. "Defiance has been a part of the fabric for a long time and that is concerning."
The judge talked about how she showed up to a meeting with the FBI wearing a T-shirt that said, "Sniper don't run, you'll die trying."
The judge also mentioned how investigators tried to stop Conley with multiple warnings that following through on her plans could lead to her arrest.
She responded with, "I'd rather go to prison than do nothing," according to Moore.
The judge also expressed alarm about Conley's other preoccupations.
"What am I to do about this obsession with the military?" Moore said.
He said Conley planned to be a police officer and join the military and then went to training with U.S. Army Explorers to learn military skills.
What if one reason she desired to go to Syria to marry an ISIS fighter wasn't just because she shared a belief in jihad, but "because he was attractive to her because he was a soldier?" the judge asked.
The judge noted that Conley still signs letters "behind enemy lines."
A female imam went to mentor Conley in jail and reported that Conley wanted to talk about violent jihad.
The judge said it's surprising that Conley suddenly is disavowing jihad and that she has seemed to do a 180-degree turn in a very short period.
The judge also brought up a letter Conley wrote to a friend that seemed to mock the American people's concern about terrorism.
Criticism of CNN jailhouse visit
Moore also referenced comments that Conley made to CNN when it visited her a day before Friday's sentencing.
Conley told CNN of her new adopted Muslim name, a new hairstyle for the sentencing date, and how "I'm in a vulnerable place right now, and it would be stupid of me to talk to you when I'm vulnerable."
On Friday, Moore noted that "she doesn't get it."
"She's a look-at-me girl," Moore continued, and he referenced the CNN interview.
Pipen said he was furious about the jailhouse visit and said he thought it was sneaky.
The judge also cited the ISIS fighter whom she was to marry, Yousr Mouelhi, a 32-year-old Tunisian man
"Why did she think Mouelhi was a good man?... Does she get this?" the judge said. He indicated that Conley still calls her suitor "a good man."
Arrested on the jetway
Conley attracted national attention last year after authorities arrested her
at Denver International Airport. Investigators said she told them she was going to Turkey to await word from an ISIS member in Syria
, a man she met on the Internet and planned to marry.
According to court documents, she intended to become a nurse in an ISIS camp. She is a Colorado certified nurse's aide.
Her parents, Ana Maria and John Conley, were aware of their daughter's conversion to Islam but didn't know about her interest in extreme Islam or jihad.
John Conley reportedly caught his daughter talking to her ISIS "suitor" on Skype. The couple asked for the father's blessing, but he said no.
On April 1, the father called the FBI to report that he had found her ticket for an April 8 flight to Turkey on his desk.