This is rather long and rather confusing, can u help?

well, my mom bought the house we live in 30 years ago, and so did our across the street neighbor, they had been friends and my sister and her daughter grew up together, well my sister is left and her daughter lives by here, anyway. her daughter has a 4 year old daughter and when she had her i just adored her because she was such a cute baby, but, now, she is rather bratty and i still have to go see her when she visits, now she visits for like two weeks at a time and i have to practically babysit her for free untill about 11 at night! its allot of stress on me because she never sits down. now the reall problem is that i have to see her everyday when she is here and i really would rather not, is there anyway i can do this without being rude or upseting people, she is practically glued to my hip, and her grandmother expects me to fawn all over her since i did when she was a little baby. i cant get the grandma mad at me because then my mom will be mad at me and all hell will have broken loose. what do you think i should do? thanks.