Biting

My girl is super sweet but does have a temper. She is mostly around her older two cousins (3.5 and 7.5) who are very ill mannered and have very little structure or self control (parents fault, not theirs). On Saturday she was with her cousin that is 3 months younger and she lashed out and clawed her face and then bit her twice- this is the first time she has ever bit. And my niece wasn’t doing anything and had no idea what to even do except cry. Obviously there is a need to correct this behavior because I don’t want her to get into the habit of doing it every time she doesn’t like something or has to share.

Does anyone have any recommendations for this behavior? I never had this issue with my 12 yr old so I’m really not sure what I’m doing.