Sure, she ignores personal boundaries and she's manipulative. But I don't see her telling Mike (if she did) about Lena's affairs in order to make herself look as the better girl in his eyes. I just don't see Ivy giving a fuck about Mike's opinion on her or making an effort to improve her odds to have sex with him again at the cost of Lena's. I see it more likely her just being gossipy or talking about Lena's exploits in a "don't get cocky kid, my Lena gets around, you're not special" way.
But lacking Ivy's pov about her real motivations, who knows?, we can just guess.