Here's a few things I see:
-you're arching your lower back, and that disrupts your ability to fluently absorb her movement.
-roll your shoulders back, at some points you look a little hunchy.
-similar to the lower back, try to bring your hips under you more. Your shoulder, hip, and heel should all be on the same line.
-try to loosen your shoulders and upper arms.
-keep your toes pointing straight instead of out. This will release the tension you are holding in your leg.
-lighten up on the inside rein when possible, the outside rein is traditionally the "dominant" rein.
-at the canter, you should be sitting deeper and leaning back more.
I'd like to see you focusing more on her hind end and shoulders than her head placement. Her hind isn't as active as it could be, and sometimes she looks blocked on her left shoulder. See if you can lift her off that shoulder by pressing with your left heel instead, or do a turn on the haunches. Remember that counter-bend can also be useful instead of just true bend and straight. Can't really tell, but sometimes it looks like she's getting away with whatever pace and gait she wants instead of you controlling it.
Those are the points that pop out to me, you have a strong point about keeping the line from her mouth to your elbow the same.
"The trouble with the world is that the stupid are certain and the intelligent are full of doubt"