Wow!, she sounds disturbing/disturbed, your paying her to basically off load on you.
She sounds like she is high most of the time, her behaviour sounds very typically drug induced.
I would be nervous of her reaction of you dropping her considering what you know about her.
Hopefully though she will understand it's no good for either of you.
But hey this is just an opinion.
Do what feels right, if your needs are not being met it's probably time to look to a place they can be met.