Toddler with super thin hair.?

My little girl is almost 2 1/2 and has super thin brittle hair. We've tried a ton of products nothing seems to help. She's only had her bangs cut and ends trimmed, never had a real haircut. We're debating on cutting her hair short in hopes it will grow back healthier. Right now it's super thin and almost hay-like. It frizzes super bad whenever we're in the car seat and goes everywhere. I'm attaching a few pictures so you can see what it usually looks like. Any advise would be appreciated.