Should I be mad or not? Because I am and he doesn't think i should be.

I am in Afghanistan for 9 months and my husband is at home with our 3 kids. he had a friend a female move in to help him out with the kids. Before she came i told him that I was not ok with it, but he still had her come. i am so mad about it and i am not sure that I will be able to forgive him, but it is hard becasue we do have 3 kids. any suggestions on what i should do?