I agree with Li, a counsellor can be a great help, but with the situation you are in now, and how to deal with yourself.
If I understand it correctly, you feel bad because of your house mate (there can be more reasons, but I think focussing on this particular one since it is so clear can be a help for you). You said she hasn't got any friends etc. Is there a possibility to go out together, do something, make new friends etc? Or invite your neighbours over. Things like that can make her happy, show her that you care and are her friend, plus it will give you a good feeling as well because you are helping.
There are many more things you can do, and I would love to help you out. One thing you could start with right away is writing down what is bothering you. It will help, trust me. You don't have to post it online, feel free to keep it to yourself, but I do encourage you to bring it out into the open, as there will be a lot of people willing to help.
All the best!
Acceptance is the key
The Outside is but a reflection of our Inside. Smile, and the Universe will smile back.
Try to keep smiling! :)