Family Members

I'm seriously getting pissed out by a few of mine own family members. Let's start with my 10 year old niece, we'll call her Susie*. Now, Susie may look all innocent and kind but she's not. She's rude, spoiled and doesn't care about anyone else except for her mother. She's been living with us for 3 and a half months now which has been hell. We've done nothing but be nice to her the whole entire time she's been here. And what do we get in return? A spoiled little brat who has a smart mouth. I can write a list of all the nice things that I've done for her:
1. Get her up early in the morning for school every day. And help her with her school work.
2. Share my room (which has been REALLY hard to do)
3. Share my covers
4. I've also had to share some of the food that I eat
5. I've bought her things like food for one and a nice birthday card but she just left it in the basement. (she said that she never got a chance to get it yet she's had three and a half months worth of time to get it out of our basement.)
6. Helped her get on the bus on time (this was before she decided to be home-schooled) (standing out in the cold was unbearable but I did it because I cared about her. But, now I'm not so sure.)
7. Not beating the living hell out of her on MANY occasions.

Now onto my younger cousin, she's 9. Let's call her Catherine. When she's over here, she acts a lot like Susie. Stuck up, rude, and annoying. But when Susie is away from her it's like she changes personalities or something. She's becomes kind, sweet, and helpful. I'm about ready to seriously end my aunt/older cousin relationship with both of them. I know that sounds weird but I don't see it that way. Finally being able to express my opinion has made me feel a lot better. This is just a rant so ignore it if you want.