This fat girl likes me... but i dont like her. Girls helpp.?

Okay now i meat this girl at the first day of school. She tried to open a convo, but i rejected it. Now she is like 5.4 over 200 pounds. 4 months has passed from the first day we talk a lil. But im not really into her, but she LOVEES me. I don't really like her. She is poking me all the time in class. I come to class i don't say hi she is like you forgot to say hi. She even told her friends about it. She does this all the time, i walk with my friend then she just hits my bag back saying HII my name. She is not cute. i dont like her because she is fat or ugly. She has a really bad personality. I found out that she lives infront in frontouse -___-. There is this other girl that i really like. If i get a good chance i would menshion her infront of her. Please help me girls. Guys she wouldn not want to have sex.