I had that happen too with a female I introduced to a different female that had been with another male. The male litterally ran at her and tried to attack her. I did the same thing you did and waited a few days reintroduced her and the male was fine with her. She wasn't receptive but he didn't try to attack her either...just checked her out and tried to grab her tail and work his way up. She wasn't ready and nipped him back. Sounds like she still had the other male's scent on her.