I don't think you're selfish at all.. if anything your dad is!
When your parents divorce, regardless of circumstances or how you feel about it, it takes a while to get used to one of them being with somebody else!
I think it's wrong to announce suddenly that a woman will be moving into your home for a month.. Your dad should be taking things slowly and ensuring you are comfortable with everything. Maybe a meeting or two but not having move into your space straight away.. Tbh, I would have thought the woman would have felt the need to make sure you were ok with things first too.
I think you should talk to your dad about it.. Hope everything turns out ok for you Caitlin
