Couldn't think of where to put it - so it goes here.

My fiance's derpy sister in law has moved in with us. She and I have a 6 year history of pretty much hating each other. She is narcissistic and only talks about herself - I don't joke about this. She owns a house [she is 28/29 years old] and just got back from a 6 month stay in Hawaii while she rented her house out.

My fiance came to me saying she is going to crash with us for a week or two until she ships off to Europe. I thought he meant she was going to have another stay over there, turns out it was only a 16 day vacation for her. While she was here we heard nothing but Europe this and that. We both got very sick of listening to it. It got to the point I avoided talking to her. Her brother and I have been together 7 years and she doesn't know who I am or where I come from. She knows nothing about me at all, because the only time we talk it's about shallow observations of her own life as told according to her.

That week she stayed with us before heading out to Europe was agonizing for me. I have social anxiety and being around someone who openly judges people drove me to feel very uncomfortable in my own house. To cut the long *** story short I will ask who ever reads this for advice, for it is much needed.
She is a stuckup, selfish *****. She doesn't buy groceries but drinks our milk, eats our food and fruit [which really pisses me off since it's expensive.] Then leaves the dishes beside the sink to have the food caked onto it for when I am ready to wash them. OR in her room [the guest room] I found a plate with sauce dried on it.

She is a messy person, she leaves her wet towel on her bed [a mattress I just purchased a few months ago AHHH], makes a wet mess in the bathroom while showering, even leaves dirty pots on the stove. This is MY house. MY way of living. Not hers. But the ***** is so sensitive if I say something she will probably go crying to mommy then I'll hear about later on.

I never wanted her here but apparently she has moved in. Without my consent. I wasn't there for the verbal confirmation of that decision between her and her brother, so my loss I guess. Everything about her makes me mad.

She even let my indoor cat get out of the house [first time this cat has ever escaped..] after I told her twice not to leave the door open. I also told her I don't like wet towels laying around, especially on the bed. She didn't listen.

I hate her and she is staying until mid-Sept [even though her plans are never thought out and **** never follows through as first led on.] She leaves to travel the tri-state area recruiting people for her college. Then after that she will be back in time to move in for the winter. She pays us $200 a month but when we had a year long stay in her house [as she offered 5 years ago] she charge us 400 a month PLUS half of the electric and heat.

Here she doesn't pay for her food, electric, internet and even uses my netflix. What do you think...? Or what would you do..?