It's rare to sex a sex link wrong, thus their name.
Usually, hens are the ones picking on each other.
What did she say that led her to believe "he" is a rooster? Feather shape? Comb size?
Interesting...
Oh, and about her attitude. Maybe she's just hitting a grumpy, teenage year. Chickens establish a pecking order, and it may look like it hurts them badly, but it's their nature. They'll survive, usually...