Should I tell my friend?

[K]

My friend Rachel (fake name) has been seeing this guy Kevin (fake name) for a couple of months now.We were all co-workers at one point, but then she got fired and a few weeks later, he got fired. At first, they were mainly just friends with benefits and they lived together. It would seem like he was using her for her car, but he would convince her that it was fine since he paid for the gas. She's moved out and back in with her mom, but she said they might end up making things "official" soon. She was REALLY excited about it. I always had bad feelings about Kevin. I'd see him at work flirting with other female employees when Rachel wasn't working and she'd confront him about it and he'd always want to know who told her that, but she wouldn't ever tell him. I feel so bad for her because she really likes him and admitted she may be falling for him. I warned her to be careful.

Well, I just found his Facebook. They're not friends on Facebook and she might not even know he has one, as his name on Facebook is different from his real name..it's a nickname with his last name. He's stupid enough to have fellow co-workers as friends on Facebook, though. Anyways, some girl called him "babe" and "baby" just 13 hours ago and her profile says she's "in a relationship."

Should I tell my friend? Rachel is 19, Kevin is 29..not quite sure how old the other girl is.