lost girl and role model

On saturday i lost my hero, the late great phil odonnell his death has really depressed me at time where i was depressed enough i want to win my girlfriend back in phil honour heres the story of me and my now ex.
Basically on boxing day there i got dumped, by my girlfriend of 6 months, shes went back to her who text her on christmas day telling her he had feelings for her. Sounds fair enough to move on in life.
But she's going from a sexual relationship to hanging around a group of kids 15ish, 2 years her young, i feel i can save her from ruining her life.
I still have massive feelings for her and well narrowlly kept her as a pal.
I intend to look about for a girl but i wanna be with her, so do i play the mate role and slag off her boyfriend at every given chance, do i bide my time in hope for my turn to come again, do i just leave it or do i play mind games and create unease between them as she still has feelings for me.

thoughts people
thanks for your time :)