Has she ever been able to sleep in your room/bed? If yes, this will be a harder road for you to fix because she knows that being in your room is an option and she will protest for it pretty hard. She needs to know its just not an option. I think at this point you have to go back to similar sleep strategies that you would have used when she was a baby/toddler. Do you watch Super Nanny? They do the silent return to bed method for this type of issue. You put her in bed and tell her the rules are: stay in bed, be quiet, lay down and shut your eyes. (my son often tells me he is not tired, and I say thats OK! you dont have to sleep, but you do have to... then I recite the rules again). If she gets up once you tell her "its time for sleep now, good night" and return her to her bed. Everytime she gets up after that you return her to her bed without saying anything at all. No interaction. This is important, she has to learn she wont get any attention, positive or negative, from getting out of her bed. Then prepare to return her to her bed a few dozen times. The first few nights it may take a few hours. After a week or so, if you are very consistent with this method, she should stay put. YOu have to be prepared for a few stressful nights of crying but in the long run you will all get a better night sleep. You must be consistant. If you cave in, even once, you are back to the beginning. I have never allowed my son to sleep in my room because I know that he is not one of those kids that can do anything "sometimes". If he does it once, he will want to do it again and again and I would never be able to get him sleeping in his own room.
If she is having fears of being alone, try to address those with her first. For example, my son went through a period of being afraid of shadows, so we would make a game of it. We looked at shadows in his room and tried to find the objects that made them. Then we made our own with our bodies and other toys and stuff. Then I gave him a flashlight to keep by his bed at night in case he wanted to "see what something was" which helped calm his fears. He also got afraid of the dark for a while, so we let him keep his bedroom door open and we kept the hall light on (previously door was closed but he did have a nightlight).
Last, is she getting enough sleep? Overtired children often wake during the night. Sometimes the best way to stop night waking is to make bed time earlier! We had some issues about a month ago with night waking and waking too early in the morning. I moved his bedtime up by 30minutes and a week later the issues were gone. He was sleeping better at nigth, staying alseep longer in the morning and even napping better during the day!
Good luck. A good nights sleep is important for everyone in the family to be at their best!