Since this is a TB, the best advice I can give you is to break everything down into steps for her. While most are very quick learners, they also get easily frustrated if they do not understand what you want.
I would say, yes to your question about not jumping her until you have 3 solid gaits going. Ideally she should be able to canter around on a loose rein without you having to her up for balance. She needs to understand that she is responsible for holding her own balance. Ideally she should have the opportunity to find her own balance at W/T/C on the longe without having to carry a rider on her back. Then let her find it with you up there. Just take it in steps. Don't move onto B until she's A, you get the idea.
Once you get back to jumping, first place poles on the ground for her to W/T/C over. Again...steps. Don't trot over them until she can walk over them calmly and so on. Place the poles 9' apart to accomodate all 3 gaits. If not doing canter, set them at 4'6" for trotting. Once she's okay with them on the ground, keep at least 2 of them set at trot distance and then put a small cross rail up 9' after them. Trot in and let her pick up canter on the other side of the cross rail. Again...take it in steps. If she does great with one cross rail, add a low vertical 18" beyond the cross rail. Jumps set in up in gymnastic lines help horses learn to find the distances and where to place their feet effectively. Single jumps usually just stress the young horses out.
Toss any notions of set timelines from your agenda. She'll get there when she gets there. You cannot rush it, so just be patient and consistent until she's ready to move onto the next thing you want to teach her. Sounds like you want to do what's right for her which is the most important part of this equation. Good luck!
You just have to see your distance...you don't have to like it.