if I told her i liked her but then rejected me...
but then i go out with someone else would she still be jealous? girl's opinion more appreciated thanks.
As in she rejected you?
She might feel jealous for one reason or another, but hopefully she'd know that it's absolutely none of her business.
what is this high school?
It's possible she would get jealous but that's not what you ought to be aiming for. If a girl rejects you, move on. If you try to pick her jealousy, she'll only come back for attention cause she knows you'll give it to her.
If she gets jealous then have her suck your dick.