Lazy Little Cousin!! Help!?

My cousin is 3 years old and all she does is watch tv, its so annoying! If she starts to cry then her mother turns on the tv again and my cousin sits there sucking her thumb and twirling her hair! There not active at all!!! When i go over there for a day i get so mad because all we do is watch Dora, Sponge Bob, Yo Gabba Gabba! How do i tell her that im bored or say politely that she should stop watching tv all the time?