When something doesn't feel right.

We've all experienced that feeling before. It sits in the back of your mind, makes your stomach feel unsettled, makes you constantly anxious. It's the feeling when you know something isn't right and you know in time you will have to make a decision. However there is always one element that prevents you from easily making that decision. Here is my scenario:
I moved to Seattle a couple of weeks ago and moved straight into a house that i got from craigslist. The ad on craigslist advertised a cute little house in North Seattle with two girls who liked to cook, listen to music, drink wine and keep the place looking cute. They also assured me that they were willing to take me around and help me out a bit considering this was my first time in America. However....
Things haven't exactly turned out this way. One of the girls i live with has just announced she has depression. I had already guessed this was the case when she would go to bed at 4am in the morning after watching television on her laptop and not wake up till 2 or 3pm in the afternoon only to go straight to her job at a restaurant. She has also constantly being smoking pot which i am not the biggest fan of. It seems she is always getting high and the smell of pot is stinking the house out. I am finding it really hard to make any sort of connection with her and it is really hard when i don't really know anyone in the city. I find myself feeling more alone and it is this feeling that makes me question my move here. But i musn't let this effect me. Without this problem in the equation i feel great. It isn't until i return home from a day out and about that i start to worry and feel more frustrated. So the easy and simple answer seems to be to move, however, this is where that other element messes with the equation.....
Kate. My other roomate is pretty much amazing. We have already clicked and are quickly becoming the closest of friends. We do everything together. When she isn't working she is taking me around, listening to music and cooking with me, going out for coffee and taking me to see live music. She really is quite the catch and a great person to live with. So it is hard to decide whether i should leave her. I know that if i move into another place i will most likely meet some new people as well that can introduce me to other people and hopefully i won't feel the same way that i do now with my current roommate. I know Kate and I will still be close even if i do move out which makes me think i should go ahead and do it. Still these little decisions in life aren't easy, what would you do?