"I actually think he's kind of lost it a little bit," Jenner, 26, said on the Kidd Kraddick in the Morning radio show Wednesday.
PHOTOS: How The Hills stars have changed
The new issue of Us Weekly reports Pratt, 26, has major rage issues. On the May 11 episode of The Hills, he had a violent outburst after Heidi's sister Holly confronted him about a crude remark he made about their mother being "just a vagina."
Said Jenner, "Lately, it hard for me -- even as someone who used to be best friends with him -- to see what's real and what's not as far as he goes... I see he wants attention."
PHOTOS: Spencer and Heidi's drama-filled wedding
Jenner also said Pratt "got all crazy with those crystals," on which Us Weekly has reported the Pratts have spent $400,000.
Us Weekly also reports that the couple are in "panic mode" about losing their source of income because neither has taped since Mid-April. (Spencer was suspended from the MTV hit after threatening to kill a producer; Heidi's role was reduced after she objected to a faux-divorce story line.)
A source tells Us Weekly show creator Adam DiVello "said he doesn't think Heidi and Spencer will come back for the series finale."
VIDEO: Spencer makes Holly's sister cry
For more - including how Heidi hasn't spoken to her mom since the premiere; how Spencer has "preyed" on Heidi's insecurities and ruined her self-esteem; how pals fear Spencer could "snap at any minute" and how their sad, desperate hunger for fame has left them friendless ("No one ever visits," says a source) - pick up the new Us Weekly today!
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