Sometimes your wife or girlfriend shows love and respect, but once you make a mistake or make her feel bad, she will yell at you or beat you because of her short-term temper.
Anger issues are psychological and may have various reasons, like childhood trauma or stress in life.
No matter the reasons, any kind of physical abuse is unacceptable in a relationship.
She may say sorry and never be angry again, but that’s a lie.
Seek counseling for her, or get out of the relationship sooner.