My best friends gf is a BITCH

My best best best friend started dating this girl and they’d been together for 4 months and they had sex a few times and then he found out she had been talking to her ex the ENTIRE TIME that they dated...she was telling him things like “I wish we never broke up” “I still love you” and “I still want a future with you” and he would say it all back. So they broke up. BUT now they’re back together as of one month after they broke up. And I do NOT like her at all. My best friend was broken, calling me at 2am crying and telling me that he felt like his heart had just been ripped out and he couldn’t believe he lost his virginity to her and this stuff...she doesn’t deserve him and but I also can’t control his choices, I just want him to be happy, is it bad that I hate her still even tho they made up or whatever?