How do I ask my bestfriend to move out without being rude but being firm.?

My friend has slowly started to move into my house with out really getting permission. First it was just staying here a night or two a week but now she is here on a nightly basis. She doesn't help much with chores, finances, or groceries but she does watch my kids at the drop of a hat. I have not asked for money bc she is havig a hard time herself, She has her own place 1 street over but it has no hot water and no heat. I have started to see a new guy and we are getting serious and are talking of living together. We feel that we have no time to ourselves and no time to be intimate bc she is always around. We are worried that she will start to cause problems with our relationship. I want to help her but I dont want her to be a wanderer or loafer.