Sitting next to the former first lady in a joint interview with CNN Special Correspondent Jamie Gangel, Bush cautioned his mom when she was asked what she really thinks about the real estate titan.
"Be careful," Bush murmured to his mom.
Barbara Bush initially declined to show her true feelings about Trump, the man who's been tearing into her son for more than six months as someone who's "dumb as a rock" and "low energy."
But then she changed her mind. She's "sick of him."
"He doesn't give many answers to how he would solve problems. He sort of makes faces and says insulting things," Barbara Bush said about Trump. "He's said terrible things about women, terrible things about the military. I don't understand why people are for him, for that reason."
"I'm a woman," she added. "I'm not crazy about what he says about women."
For his part, Bush has mounted an aggressive attack campaign against Trump this winter, saying the GOP billionaire has "hijacked the conservative cause" and repeatedly calls him a "jerk" for "disparaging" a long list of people, including Hispanics, women, and people with disabilities.
It's part of a strategy to make Bush the anti-Trump candidate in hopes that Republicans who oppose the top tier candidate will unite behind the former governor. Bush regularly boasts that he's the only candidate willing to take Trump head-on, though other candidates, especially Ted Cruz, have started mounting attacks as well.
Asked if she had anything more to say about Trump, Barbara Bush said she didn't want him on her mind.
"No. I do not. I don't even think about him," she said. "I'm sick of him. That's very strong."
Interjecting, Bush again playfully warned his mom to "be careful."
"That's my job," he said about attacking Trump. "Everyone else is in the witness protection -- I want you to stay in there too."
Trump fired back Saturday morning, taunting Bush for having "mommy" take on the GOP front-runner.
"Wow, Jeb Bush, whose campaign is a total disaster, had to bring in mommy to take a slap at me. Not nice!" Trump said.
Barbara Bush -- the matriarch of the Bush family who's the wife of a former president and mother of another --appeared at a town hall for her son in Derry, New Hampshire, Thursday night. The cameo came just a couple of weeks after she appeared in a campaign video for Bush as well.
Trump has already criticized Bush for trying to bring his "mommy" out to help, and Bush will likely take more heat from critics who are averse to political dynasties and don't want to see another Bush in office.
The barbs worked both ways, however. When Trump's plane was delayed by snow
and he had to cancel an event in New Hampshire, Jeb Bush tweeted a photo of his mother in New Hampshire at Trump and pointed out that snow didn't keep the 90-year-old from the campaign trail like it did the billionaire with the private plane.
Barbara Bush said she "has faith" that her son, who placed a disappointing sixth in the Iowa caucuses, will prevail.
"I'd like to remind you George Bush came out of Iowa with 'Big Mo' and then there was no 'mo' after that," she said, talking about George H.W. Bush's 1980 victory in Iowa, only to lose the nomination to Ronald Reagan. "So remember the campaign has just started."
Jeb Bush grew emotional Thursday night at the town hall with his mother by his side when he talked about his "idyllic" father, whose health, at 91, makes it difficult for him to go out in public.
New Hampshire voters routinely ask Jeb Bush about his parents, who spend part of the year in neighboring Maine, and like to share stories and photos from meeting them in the past.
"The connection between mom and dad and people here in the Granite State is phenomenal," Bush said. "Anybody that has lived through all these campaigns can remember having a dinner, having a picture, having a handwritten thank you note, going to Kennebunkport."
Bush said it was honor to have his mother come out in support of him and "relive all those things that she used to do" while campaigning for her husband and son.
"It was a big sacrifice," Bush said.
But Barbara Bush protested: "It was no sacrifice. Trust me. It was a great treat."
"I adore my child. Every mother in New Hampshire knows why I'm here," she later added. "They know."