It’s great to hear of the progress!!
Sometimes, XC jumps have a different shape/topline than stadium jumps, and it can be very helpful to recreate the shape/question in a stadium setting with tiny jumps that are portable and fall down if needed–especially with a less confident horse.
For instance, I have a gelding I got straight off the track, who at the beginning of his jumping career was super confused by anything that wasn’t a crossrail or straight horizontal across the top. He just didn’t seem to realize it was a jump, even though he was jumping simple stadium fences nicely! I got some blocks and cones in various colors (especially black) and incorporated them into my stadium jumps. So, for instance, I’d start with a crossrail, then make it small vertical, then tuck one block underneath, then a second, then remove the jump pole and just jump the blocks or other objects. Hey, at least I knew he was looking at the top instead of the base of the jump early! Whenever I run into issues with him, I take apart whatever we’re having trouble with and redo one small step at a time. He’s got a great work ethic but is an anxious fellow and gets rattled if he feels like he’s done something “wrong.”
I’m going to fourth or fifth or whatever the neck strap. Also, her boy might get more confidence if she thinks of sinking lightly into the saddle in the stride before the fence (whether trot or canter). She will be more able to feel him and it will be easier for her to put her leg on that last stride, and less likely to tip forward and unbalance him.