My friend Susan came to my home for several times this summer holiday.She began playing my piano when she got my house and kept playing for the whole day !!!:(
So I can't practice playing when she comes to my house

Sometimes I have to finish playing some pieces of music because these are my homework,I really need to practice!!!!
If I ask Susan not to play my piano,maybe she will never came to my home,and I will be made to feel mean and unkind.
She even asked me to teach her!
What should I do?
(P.S Susan hasn't got a piano,and she never get piano lessons.I ever asked her to find a teacher and began piano lessons,but she said she did not want to spend money on learing.)