My roommate owes me $7.50 and I'm feeling the urge to let her know about it.
Why does she owe you that much?
She has refused to pay the rent for the last five months
You deserve to get some of the rent off of you, your roommate shouldn't be living there for free. She needs to pay up or get out, even if it's a very small amount like that. She is taking advantage of you.
She needs to leave all the furniture that I bought.
I'd recommend not going to far with the situation. The amount that she owes is not that much, you should give her the opportunity to pay back