How to help encourage my horse while jumping?

What I would also do is go back to the basics. Teach her do go over ground poles, and once she does that without putting up a fuss, then SLOWLY raise the height. Maybe go to a 1 ft cross rail, then a 2 ft cross rail, then a 1 ft vertical and so on. You shouldn't move up the height if your mare doesn't do the lower one perfectly.