Awww...she's a cutie!
As far as standing, you just need to do it gradually; like get her set up, asking her to "stand", but don't step away from her. For an Arab, you want those front legs and right rear set squarely under her, and the left hind slightly to her rear, and directly under her haunch (for a reference point)...alot of people 'overstretch' Arabs, but that is how they are supposed to be set. In your last photo she's pretty much ideal, her right rear just needs to be more squarely under her.
When she has her 'cue' word "Stand" down, then start taking a step away from her...if she moves, simply correct her, and try again. You want to be able to go to the end of her line (usually a 8 ft showlead), so you can stretch her neck out, and move it up and down.
When showing an Arabian, you want to show off the expression they have, so teach your mare how to 'target' a dressage whip by showing it to her, and treating her. She will eventually learn to 'follow' where ever you 'hold' the whip (be it in the air, or near the ground, so you can show off her arched neck).
When you ask her to move with you, especially at the trot, don't inhibit her motion...just let her move freely (obviously, maintain some control, so she doesn't dart in front of you, but let her 'show off'); EVERYTHING about showing an Arabian is about the expression and showy-ness of the breed! You want to exhibit her in such a way that she just 'comes alive'!