I think she's nice over the saddle, could open her hip angle a bit more so she's not laying on his neck, heels down a touch, and elbows in...nice release I think, hard to tell since the horse is so dark.
I'm not the best at critiquing but that's what I got from that pic.
Actually, I would have like to see him pushed more into the fence, so he actually had to use his hindend and abdomen to arc over the jump, not just soar over it with speed alone.
But, that's just me personally - especially since he's schooling - that would help him develope tighter knees, they're a little loose.
Your friend looks like she's ducking ever so slightly to the right, not a biggy - but it is hinder the horse to some degree. I'd like to see her elbows in and more supple ankles, otherwise she looks like a solid rider.
I would also like to see him a little closer for take-off, only about 30cm though. But I am not a fan of people getting their horses in too deep or deliberately making striding short between fences when schooling to "teach the horse to pick up" Sea To Sky is right - the bigger the fence gets the further the take-off point gets from the fence.
Horse: I think he could bring his knee's up a bit more, for that height fence I would expect them to be above the horizontal and have his lower leg a little more tucked up (but he certainly isn't jumping poorly, I would be happy watching him jump that height in that form). He looks like his neck is restricted a bit - kind of hard to tell because he is dark but it just looks like the bit is pulling on his mouth. With slightly more release those knee's might come up.
Rider: Looking slightly to the right and has gotten a bit too far forward and out of the saddle, looks as though she is gripping with her knee a bit and rotating from there, needs to open hip angle a bit more. Apart from release being possibly a bit short it is being given very nicely as an automatic release (Sea To Sky ... that's the release we want you to do when we were commented on your XC photos)
Over-all a very nice picture and both horse and rider certainly don't look like they are being over-faced by this height