Cuddlepie, please just give her notice and have done with her, or if you're in real need of the money, set up a new tenant and give her notice when you're ready to move the next one in. I don't think that you two are a good match (and honestly, I'm not convinced she'd be a good match for any but the strictest, most ironhearted landlords given some of her behavior). I think that you've started off on the back foot because you muddled the waters in the business relationship from the beginning and from your last post, she views you as her naggy mother who just can't let her /be/. Her boyfriend liking her, but not liking her enough to visit her is not your problem. Her issues with her father is not your problem, and from your posts, it could be a bid for sympathy because she was a big fat jerk to you and she realised she leaped over the line with both feet.
You wouldn't be kicking her when she was down if you decided you didn't want someone throwing tantrums at you whenever she had a bad day.
So, I'd sit down and have a firm idea of what you expect from a lodger before you start advertising again. And honestly, if the price is right and you're mostly reasonable about your rules, you'll find someone who will abide by them. I think you need to be clear about what you expect from the jump. Be assertive and proactive! "We all use our own blankets if we're chilling on the sofa." "I prefer that no dishes be left out, and since we'll all be using the kitchen, we'll leave it so someone else can use it without having to clean." "This is my system for cleaning, and you can find things here, here, and here." "We keep the temperature at this level. If you want, you can pay more towards the heating and we'll decide on a temperature, or you can get an electric heater."
I also think for you, it would be best to maintain a friendly business relationship at the most. I think we're the same way in that once you get to know someone, you bend over backwards to help them if they're down. That's great for friends, but as you can see, it can bite you with things like accepting a lower rent for a good sob story. Good fences make good neighbors, and clear expectations and firm boundaries on both sides will make it so much easier for both of you. Plus, you can just relax instead of having to keep worrying about whether it's passive aggressive to put your dishes on hers, or if it's just you that doesn't like sharing blankets (you're not), or if you'll seem like a bait-and-switch if you come up with a bunch of rules now.
If you do decide to keep her (and I don't think you should.), when you talk to her on Sunday, I'd renegotiate how you're doing things and set out like she's a new tenant. Discuss what you will and won't tolerate and make it clear what will get her served notice.
Good luck to you!