This was to be expected, she's realising that this is real, so she's getting more and desperate. She will as either myself or someone else said up thread, scream more, cry more, shout more. It's the only way she knows.
This is when you really do have to draw together all your strength and stay firm and resolute. It's not easy. But you know that it's for the best that she goes. You've already had glimpses of peace and happiness when she's been away.
Joblot, if this relationship was worth anything, your best times, your times of peace and happiness would be when you were together.
You know how unhealthy this relationship is. You cannot stay in the this relationship. She's now realising that you mean business. You will probably find her behaviour alternates between being extreme and then being quite ok - saying she'll find somewhere. When she's ok - she isn't really, she's just hoping that if you see her being reasonable, you'll give in. She's trying every trick in the book to stay. She's manipulative and abusing you.
You can't change the past - you did nothing wrong in letting them move in. And you're doing nothing wrong now in wanting them to leave.
You are not a heartless ogre. If you were you wouldn't have posted your concerns in the first place. Your caring and loving nature are apparent - but she's taken advantage of you for too long.
Just keep posting on here, keep firm and tell her that you demand space from her and the relationship, to see whether you can in any way have a future of some sort together.