The Unforgivable Situation of Sarah

Sarah offered to pay half her rent if she could stay at my flat for a month. It's been more than four weeks later and there is no sign of Sarah moving out. She hasn't been to any viewings, not mentioned where or when she'll be staying somewhere else. What do I do? I want my space back but I feel really guilty for kicking out my friend. But on the other hand I feel a bit like she's leaving because she would never ask her to leave. Which makes me feel taken advantage of. Should I say what I think about the flat?! Please help! You've been so generous you've done such a fantastic host. Can you get out that