And it’s not your mates fault that she won’t let you sit... you need to build up the muscle to hold on yourself because you’re horse is not marking you not be able to sit, you just have to control her more and maybe slow her down and package her up. Hope this helps 😊
Do a half seat since she might not like the feel with you on her back.
maybe she doesn't like the feel on her back try sitting on the rail first to get her used to it
When you come up to a jump do a 10 metre circle then came back into the jump and if she rushes again do another tight 10 metre circle then she should learn to slow down before a jump