walk to the fence and canter or trot the last three/ four strides. keep doing this until she relaxes or canter around 20 ft up to the fence, halt, back up and then canter over the fence
Try riding over some ground poles in a canter, and they come at a small cross rail at a trot and ask her to canter 2 strides before the jump.
Put a pole 7 metres (7 big human steps) in front of the jump. Cantor to the jump without looking at the pole in front of it (pretend like it's not there). After a few times jumping this, she'll get it and start to cantor normally and she'll relax on that last stride. Keep the cantor and hold your hands still while riding at the jump.
Gymnastics & a lot of trot work over small jumps with a placement ground pole. Also-slowing the trot a few strides out has helped me with this issue in a horse I had. Also-use your voice to sooth.
Try lots of gymnastics and just stay over her back when you're going though it. She'll figure out really quickly that if she rushes any part of it she's gonna jump very uncomfortably. Don't set them up big, maybe 2' with some cross rails and ground poles. Say make it looks like this:
I I I X I I I X X I I
The Is are ground pole/small verticals and Xs are cross rails.
Make a two stride tiny cross rail grid, walk into it, make her halt, walk over the next ten make her halt and keep doing that down the grid until she listens to you and not focusing on the he jump, then do the same in trot. Later put the jumps up and have about 5 stride in between, make her trot or Canter over the first, halt and then let her canter over the next. This will make her listen to your aids as this is what she's ignoring, she's focusing on the jump and not you
You can work your horse on a small circle over a low fence. Make the circle smaller when your horse speeds up and larger when they slow down as a praise. Also, poles, going back to the trot and shortened low gymnastics are wonderful ways to help too.
Ask her to come back down to a walk before a jump. Walk, ask her to trot a few strides out, then ask her back down after your landing.
Lots of bounces, it forces the horse to stay at the same pace because of the closeness. If you do jumpers, go back to hunters, use corners, focus on control.
Maybe try using a different bit or double reins
Jumping gymnastics. Half halts while in the middle of jumps. Lope to jumps then completely stop before you get to them.
Put some polos in front and behind the jumps !
Bring her back down to gymnastics. Bounces. In and outs. Make sure to put canter poles before and after.