There's probably nothing less attractive on this Earth than a used-to-be super-starlet, who -- in her old age -- behaves in a way that best behooves a teenage socialite. But that's exactly the case with Demi Moore, who -- despite looking good for being 50-something -- is looking completely ugly because of her behavior when it comes to her ex-husband, Ashton Kutcher, and his soon-to-be-wife Mila Kunis!

Gossip Cop is reporting that, when Demi found out about Ashton's engagement to Mila, she called Mila on the phone, not to congratulate her, but to "warn" her that Ashton would cheat on her! (You stay classy, Demi.) "Demi doesn't care for Mila, but she felt like it was her duty to at least warn her that Ashton will always be a cheater and isn't the sweet, innocent guy he portrays himself as," reports Gossip Cop.

This would be a pretty hard thing for Demi to do, especially since Mila knew Ashton LONG BEFORE Demi ever came into the picture, and she's seen him through EVERY breakup he's had in the industry. Pretty catty -- and petty -- of Demi to do, if you ask me. And if this is how Demi behaves now, one can only imagine how she was when she was married to the guy. Yuck!

And of course, Demi continues to further make a spectacle of herself and act her shoe size, as opposed to her age: Demi was recently partying in Miami... with no less of a classy crowd than the Kardashians. And, at a recent Oscars party, she went out of her way to dodge her ex-husband and his soon-to-be... even though she had no problem calling her up earlier and blasting him.

You know... if Demi put this much effort into getting acting jobs, instead of acting like a fool, she'd probably be a respected actress instead of a tabloid punchline.

Stay classy, Demi. Stay classy.