Advice please please please! =(?

Okay so im 13, and my sister is 15 and recently my cousin moved into are guest room because problems with her family (long story) anyway, she is reallllly starting to annoy me! She comes into my room in the middle of the night and will be like EMILIE!!!! and when i finally get up she'll be like nevermind, i hate you! It seriously happens everynight. Then sometimes she will be like can you come with me to get a drink, get food,go to the bathroom..and uhg shes 13 too.. she can do it by herself! me mom said that its not a big deal.. but she wakes me up everynight more then once for nothing! and it creeps me out! I told her to stop... then shes like okay.. and does it again! what should i do?!?!