Monstarbaby's Things

I have a friend. We used to be roommates, sharing one apartment. We shared the load of paying the rent and utilities.

Here's my dilemma. We are not roommates anymore. She moved out like a year ago. But she sometimes sleeps over. And I let her, because I don't want to.push her out on to the streets. Especially at nighy. However, this year, she's been staying in the apartment way often than I like. Using the electricity and water, sleeping on my bed. And she's not paying for any of these. She knows of my financial situation.
I just received the bill for the electricity and water today. The expense is too much for me to pay. I just came home from work, tired. And I see the bedroom looking like a mess. My blanket on the floor, my stuff chucked unto corners. And I just wanna cry. Because I knew she stayed over the weekend without my permission again. And she left the only space I could deflate after a tiring day of work like a pigsty.
I am offended. I want to say something but I don't want to jeopardise this little friendship we got going on. But at the same time I find the situation very unfair.