ADHD &/or Anxiety

My 5.5 year old dd is an amazing kid! She is also hyperactive and impulsive at times. She went through a neuropsych eval., where they reported that she had "ADHD tendencies", and suggested stimulant meds. She's been on Adderall for about 6 months, which has helped her in quite a few areas. She tolerates it well and definitely calms down and is better able to focus. She also has some sensory issues. But, she also seems to have an anxiety component. She never had a care in the world until she hit 4 years old. She did not follow the rules, she could not control her behavior. She was outgoing and happy all of the time. But, at 4, she slowly became more and more anxious. Now, at 5.5 years old, she is a worry wart. She has a lot of trouble sleeping, because she worries (mostly about noises). She is often tired during the day. I give her Melatonin, which definitely helps her get to sleep. She bites her nails a lot, and chews on her fingers at times. She analyzes most things. She has become an extreme rule follower. It's gotten progressively worse. Today, we went to the pool, which she loves. About 3 months ago, she decided that she does not want to touch the locker room floor, so she wears water shoes just for the locker room. It is a phobia to her. She thinks the water, hair and dirt on the floor are gross (agreed). Today, she kept staring at the lifeguards, and didn't swim much. She would not jump in the pool until the lifeguards were not watching. She stood biting her nails most of the time. The lifeguards were on the other side of the pool, and watching our general area, because that's where all the kids were. I asked her what the problem was, and she said that the lifeguards were watching her. She was afraid she would get in trouble. So, we walked over to the lifeguards and I had them tell her that they were not watching her and that she was doing a great job and could swim and jump as much as she wanted. She relaxed a bit, but was still a bit nervous. She has done a complete 180 in terms of her fear of doing something wrong. She gets nervous if a car is 2 blocks away, she worries about most things. She couldn't play soccer last year, because she heard all the people yelling and watching her. I had assumed that it was the ADHD, her inability to filter all of the stimuli coming at her. But, maybe it was more anxiety? My question is, how do I figure out what the true problem is? How do I know if it is really just anxiety, ADHD with anxiety, or just ADHD. Do doctors treat anxiety with medication at this age? Do kids get put on stimulants and anxiety meds? I don't want her to drugged too much, but it kills me to think of her worrying all of the time. She's not incapacitated by the worry. She is still very outgoing and has fun. But I can't bear the thought of her worrying about so much.