Trump supported Knox while she was imprisoned in Italy in the murder of her roommate.
A real estate investor and friend of the president who lives in Trump Tower says Donald Trump is furious with Amanda Knox.
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"The president is 'very upset' with the ingratitude of Ms. Knox," George Lombardi told The New York Times.
Trump feels betrayed because he had publicly supported Knox while she was imprisoned in Italy, according to Lombardi, yet she wound up endorsing Hillary Clinton during last year's presidential campaign.
In 2007, Knox was notoriously photographed kissing then-boyfriend Raffaele Sollecito outside the crime scene in Italy after her roommate Meredith Kercher was found murdered.
"Considering the fact that she never thanked [Trump] for the help he gave her and the family, at least a thank you note, or some kind of acknowledgment for what he did for her would have been appreciated," Lombardi told Inside Edition.
She spent four years in prison — and Trump came out as a vocal supporter in 2011.
"She's not guilty, she's been persecuted for no reason," Trump said at the time. "Amanda Knox is not guilty."
In September 2011, Trump also wrote on Twitter, "Everyone should boycott Italy if Amanda Knox is not freed---she is totally innocent."
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An emotional Knox finally came home to Seattle after being found not guilty in 2015 at her second trial
She now writes a column for the West Seattle Herald.
In a column that appeared in the paper, she endorsed Clinton, saying of Trump: “He is inexperienced, uninformed, and irresponsible (to say the very least).”
Lombardi said president will likely remember whose side Knox was on.
"If you're businessman in New York, you swim with the sharks. You don't forget."
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