Renting two rooms in my townhome to two girls. The contract goes until Aug, then month to month. One girl I'm letting stay, the other I don't care for... she's kind of white trash and so are all her friends she always brings around. How do I politely tell her I'm not renewing her contract, but letting the other girl stay, without it sounding personal?

(I"ve already checked my state laws and I can not renew it if I choose)