[Fathom Zero]

It depends on how she feels about this other cat. If it's legitimate romantic love, then you can't compete because you'll risk losing. She'll just have to decide when to ditch 'im, if ever. If it's not love, then just wait until she moves onto the next guy, which should be you, providing you position yourself and want it.

If this is a competition, then she is a prize. It's a game where your objective is to beat the other guy and claim what's yours.