Male cat attacking female

My mom and I have 3 cats, a 3 year old female, and a 2 year old male, along with their 1 year old daughter. The male is fixed, however our female is not. We have noticed that he randomly attacks the female, very aggressively. It causes them both to lose hair chunks, along with my female cat being always timid and scared. I feel bad for her, they all are very friendly ultimately but she’s been distant and skittish. Please let me know maybe some suggestions on how to stop this? Or maybe even a cause? She’s scheduled to be spayed in the next month.