You are feeding into the problem, probably she likes having you with her, and knows you will stay if she makes enough bother over it , Try the other tack, and unless you want her to sleep with you, leave her in her own room each night ,you will get resistance at first and she will act out but if you can be consistant she will get used to it, I have seen this many times and the more she believes you want her to sleep in her own bed the more things like the Bathroom and laying there with her or a drink , she will come up with. Be tough and be consistant you can leave a hall light on and let her read. However if you want to let her sleep with you its okay a lot of Families prefer it. Check with the prescibing Doctor that the med is suitable for her as sometimes they can work the other way.
Your daughter is 11 years old and takes medication for anxiety. But, anxiety medication is used to "take off the edge" of a person's fears so that proper therapy (as CBT - cognitive behavioural therapy) and/or intervention (as worry desensitization) methods work. These are the tools to help your daughter learn how to manage her fears/anxieties; the medication only supports or assists therapy/intervention. I really think you need to speak to your daughter's doctor about getting help in this area - perhaps ask for a referral to a child psychologist or someone with experience in anxiety issues. There is hope for children suffering from anxiety but do note that the teenage years are especially difficult to treat (not sure why). Hope this helps ...