Is it normal that my girlfriend bites and scratches me when she cums

Basically when we have sex and I make her cum she bites or scratches me, most of the time it's biting. She draws blood but when she does she stops and sort of comes back to the real world and instantly says sorry and like tries to do anything to get me to accept it (the apology), I used to think it was because her orgasm; like she would lose her herself so much that crazy stuff happens, but I'm starting to doubt this.