I love the school horse in this vid - dead honest, cute jumper and still has a little energy to him. I would want him in my barn. *Wonderful* horse to learn on.
Mostly agree with the other posters. Your friend has a lot of potential as a rider. She seems brave and athletic, but she needs to solidify her basics before she goes further with her riding. First is the lower leg. Perhaps a shorter stirrup, but then, lots of work in two point and without stirrups to get it rock solid underneath her. Positioning the foot in the stirrup correctly as drafteventer suggests will help as well.
Second, she either needs to learn the following seat at the canter OR stay in a two point. The most distracting part of the video was her attempt to sit the canter in the turns. I'm sure she felt the need to sit up and balance in the tight space as the horse has a little "go" to him; but a three point seat rather than a full seat would work better until she learns a following seat.
Once her leg is solid she can polish her position in the air and work on letting the horse close her angles while her upper body stays still. Gymnastics are a huge help with this. Jumping through a long grid and attempting to do as little as possible and *feeling* the horse's jump close your angles is invaluable.
I disagree with some of the other posters about the release. While it's perfectly fine/non abusive for this level and this size fence, a rider at this level should be practicing moving her hands forward and digging her knuckles into the neck as the horse takes off and picking the contact back up on landing. Her hands stay in the same place and just take a little support from the neck in the air - again, not restricting him at this height, but she needs to practice a real release for when the fences go up.
Unlocking her elbow and allowing her hand and arm to release will also help her leave her upper body still. Right now it looks as if her torso and shoulder is trying to do the work of the hand and arm.