If you've only had her for a day, she needs some quiet time alone in her cage just to get used to the new surroundings without an aggressive male coming after her already. Give her a little time to adjust before putting them together.
Do you play with your male and take him out of the cage? if yes than he probably thinks YOU are his mate. Lovebirds DO NOT need to be kept in pairs. Separate them, play with them and let them together outside their cages. under supervision of course.
Try introducing the bird together in neutral territory, like a room neither have been in before. Re-arrange the cage so they think its a new one. Separate them for now so they don't fight as fights can get nasty and you can lose one.
It sounds like the cage is too small for a pair of lovebirds, get a newer bigger one! Way bigger one.
thanks for the feedback, it seems like they're learning to get along better now. I think they just needed some time.
I just got a female lovebird for my male lovebird but problem is my "male" lovebird keeps running after her and trying to preen her tail feathers and head but he does it harshly, he's not trying to hurt her but he's very dominant and controlling about it. She either runs away from him or takes it but he isn't hurting her because I watch them and sometimes he will step onto her (ride her basically) but he doesn't try to mate with her, it seems like he just does it to get a better grip on her so he can preen because he just stands on her and cleans her feathers, its so weird and shes way to little to mate right now anyway!
They're both in separate cages now though so don't worry about the fighting/killing, They don't really do much when they're in the same cage except he runs after her and she runs away. I've only had her for a day so maybe he just needs to warm up to her?
