I've flat ironed before as well. Start with a low temp. Mine straight iron can go up to 300 before it burns the hair, but they are all different. I then wet the hair down and put a bunch of conditioner on it, then I flat iron them.
Ya, make sure its low temp. Its really bad frizzy hair, then you can go up alittle, but not too much.
Yupp just make sure her hair is nicely coated in conditioner. Good luck!
Now what I do, I do condition my ponies manes and tails, and I rinse some of it out, but leave some in.
I shake the access water out, so its damp enough
then I flat iron...it will sizzle because its drying the hair in the process. Then I let my ponies hang dry