inherited mean cat

Question
   Hello,
I have recently inherited a cat (over 1 month ago). She is about 10 years old and is a grey Tiger cat. I have never been a cat person (infact i am slightly allergic to them) so I am unsure of the breed.
My uncle passed away about a month ago and I took Maxi in. She has always been a mean cat. She would never let anyone touch her except for my uncle. My sister was at his house EVERY DAY and maxi would hiss at her. My Nana was also at his house every day and was only able to pet her with her foot. When my uncle passed Maxi ran up to my Nana and allowed her to pet her.
So now I took her in because I didn't want a shelter to put mean Maxi cat to sleep. She usually stays under the bed. After 2 weeks she would come downstairs as long as my boyfriend and I were sitting still and not looking at her. If we said her name she would hiss and approach us as if she was going to attack us. After a little while she would let us say hello and if we looked away she would go about her buisiness. We have provided her with a feeding schedule that we stick to. Plenty of toys, a window perch (all of which she rarely touches)and I place treats in her hiding spaces throughout the house.
Just when I felt as if we were developing a relationship with her a house guest from afar started staying with us in our small 2 room studio apt. Since then Maxi rarely comes out,(even though before when visitors were over she would come out as long as no one bothered her) she started hissing at me again and has gone through fazes of not eating and vomiting. At this moment her eating seems to have stabilized but I am very concerned for her health and emotional happiness. She was sleeping on the windowsill at the end of my bed at nite but now I cannot walk into my bedroom if she is in there. She hisses and seems like she is going to attack me. I just purchased some Feliway spray after reading reviews that said it may make her feel more comfortable. Any advice you could offer would be extremely helpful. Thanks!

Answer
It sounds like she could have been abused by a former owner. I cannot  however  say this for a fact. Now, I will have to recommend the cat to see a vet for they do have cat psychologists or drugs that the cat can be on. I do not recommend drugs unless 100 percent needed. I recommend this site also for new cat owners.

http://pets.yahoo.com/pets/

Good luck and sorry I couldn't help more. See a vet.