Mami will forever be 'the ex-girlfriend(that never was)'. How and why would she still involve herself is as mysterious as the universe itself!
I really dont hate her I just want her character to properly unfold at this point. I hope deep down she's really just insecure for not seeing kazuya for who he is, or for not being able to see him like the other girls do. We know she's manipulative and uses men to her advantage since they are idiots... but she failed to notice kazuya was a special kind of fool and that excruciatingly irked her.
If its anything else i wish she'd get ruined for the evil that she is.