How to get two people to break up.?

Ok so I know i should just let them be but i cant stand it anymore. these two people have been going out for a year now and im in love with the guy. They are in love and i hate it because he is always flirting with me wen she's not around and he's always leading me on. Then when she's with him, he totally ignores me! I wanna tell her somehow but i don't know her like that. And if I try to talk to her she might tell him and he might get mad at me and deny everything. then two people will hate me. I try flirting but he doesn't seem to fall for it. I know i should leave them both alone because i want him to be happy but i hate what she's done to him. every since they started going out we've stopped talking or hanging out. He's totally dissing his friends for her. I can make him just as happy. i wouldnt care if he had other friends that are girls. i feel like he has boundaries now. ik we all should in a relationship, but it feels like she's holding him back. i just need to know how to deal with it. how to break them up. or how to get over him. pleeeeee help meeee!!