I am 5'3", 130lbs, medium bust. I have tried and tried to order dive apparel online (wetsuits, etc). My problem is that I am slightly long in the torso for my height, but fairly built in the legs and butt due to years of competitive swimming. You may get lucky trying to narrow down your options online, but for a truly good fit, you really should send her into a local dive shop and have her buy one there. I have yet to walk into a dive shop who won't price match a credible website. Even the exact same brand and size could possibly still have a slight size variance to the one tried on in the store.
You need to take a little drive over to Scubafest in Columbus Ohio in March. Wetwear will be there and taking orders for their full custom suits. Connie is a genius at getting measurements right. As is her hubby. I'll never buy another off the rack wetsuit. My 3 mil fits like a second skin and is at the same time the easiest suit I've ever owned to get on.