First, its fantastic you have the communication with her. I think thats really really positive. I hope that continues.
I have a facial PWS.
KIDS ARE HELL.
whats happening to her i think is normal. to me there is no obvious answers. All you can do is continue to love her, listen to her and reinforce all the positive things about her. As she gets older it might even get harder. I know, your a parent and won't really want to hear that but personally i think she's off to a great start. Be there when she needs a shoulder. keep her active sports hobbies etc..if she's doing something she loves she won't think of it so much until it really bothers her. educate her as much as you can so she can even explain and correct teasers. she can also ignore it if possible. while it hurt mostly thats what i did. i toughened up.
my teachers use to tell me as a response to teasing " stick and stones will break your bones but names will never hurt you" i thought that was crap LOL but that was just me.
she's still gonna grow up one day but it won't just be kids it will be adults who are hell also.
you will always worry but your doing ok so far.
Even now, i still tell myself atleast i still have both eyeballs and all my limbs intact just missing a gallbladder lol