OK, here’s the reply from my Western SS guru friend:
Well, the jacket is mahvelous. Love the detail in the back and the points on the front.
The skirt is, as all skirts are, a little tricky. You have to actually sit on the skirt when riding SS which takes up a lot of room. Then you need enough room to get your leg over the fixed pommel which then takes up a lot of length of the skirt. Depends on how tall she is, too and how much to right leg will take up in the skirt. Its also very tricky with skirts because in order to be totally safe in case there is something funky going on with the horse in all the commotion and you get unseated, you do NOT want a skirt wrapped around a pommel and you trailing under the horse. SO, anyone wearing any kind of skirt SS usually takes the left seam, splits it all the way up and then recloses it with velcro to make it a breakaway. Its a gorgeous skirt but it looks to me that it might be a tad tight for SS plus a little too short because you don’t want a bride with her knickers showing, at least not to the crowd. SS skirts are supposed to cover the feet and legs.
I might be able to put her in touch with one of the SS Mavens in her area who can give her better advice than I can on outfits. And also many of them sew. She could possibly have a similar style outfit made that would be appropriate AND fit ss riding better for about the same price as the store bought one. Most SS skirts are longer on the right side to make up for the leg over the pommel however, a ss skirt has a loop so that the excess at the knee, then comes around the back, buttons at the waist for walking and makes a bustle effect. Just a thought.
I can fwd her info to you if you’d like. 
I loff that jacket myself…