Hi! There's a YT member that goes by Chattiesmom that makes wonderful silk step-in harnesses. Everyone has great things to say about the silk step-in harnesses, and because they is silk, they are less likely to mat the hair
As far as hair accessories...The best thing you can do, if she can get barrettes out of her hair, is to buy some bands for the hair. There are so many places to buy them, that I don't even know which place to recommend.
I put a band in my girl's hair everyday, and she doesn't try to pull it out. Just make sure it's on there snug, but comfy. You don't want the hair being pulled from the eyes too much, so you don't want to put the band in all the way to the skin. Hope this helps...There's a link that has been posted before that shows how to put a topknot in their hair. Then you can add a bow or whatever you want, and hopefully it'll be on there comfortably, so she won't be trying to get it out