Got bitten by new big rat

[chase]

Got 2 rats and had them 4 couple weeks. We fell in love with the last baby girl the breeder had and put deposit on her. the breeder said u cant have her on her own so she paired her up with big older rat and she seemed fine when we held her. To cut a long story short she has been biting gently each time she comes out to play. Last night she turned her head when getting her out of her cage and she just nipped me but didnt hurt. Still took her out to play on sofa . she is really hyper and when I picked her up she bit me really hard and drew blood. Think I have done wrong thing getting her now as wonder why breeder wanted rid well actually now I know. Breeder said she had litter but killed all babies? We have had rats b4 so know that they are generally good natured. I dont even want to tame her now as terrified of her and think it is the way she is.The baby has a fine temperament but from the start kept thinking the big one had temperament issues. OH