Normally male and female bettas cannot be kept together unless it is a large tank with many hiding places.* Breeders only put the females with the males to spawn and then they are taken back out in case the male tries to kill her.* I can't say this is always the way it happens, because there are always exceptions to fish and what they will do.* It does sound though like your one male is showing this behavior, and if he doesn't kill her physically, he will probably stress her out until she dies from the stress.* If you can keep that hurt female by herself, she should heal quite nicely.* Keep your eyes on the other couple as well.* *
P.S. Welcome to FishLore! It's great to have you with us!