My best mate went out with my ex and she knew i loved him so much i was with him for 3 years bt i took her bk

because she said sorry , i know it was stupid to become her mate again buh i didnt know wah to do , buh now i dont feel right towards her with my new boyfriend and i still feel the hate for her how can i make it all go away,so i can look at her a think yer she is a good best mate