What should i do?

Hi All, my parents are visiting me from Australia this weekend. I havent seen my dad in almost a year and they are only here for 2 weekends i.e. I only get to spend 4 days with them coz i cant get any time off work. Anyway my husband is commander in the Army (although he is only a LT) and one of his friends (who happens to be in his detachment) has a girl coming to visit him this weekend. However he is being sent to training and cant be here with her. This girl isn't a girlfriend or anything like that. Anyway my husband has volunteered to look after this girl coz his friend is away and Im really pissed about it. I dont get much time to spend with my parents and now i have to babysit some random I dont even know! I know he feels obligated coz he is a commander but I dont care. Family comes first for me. And noone in the army has EVER gone out of their way for me, so i figure why should i?? Am i wrong to be like this?