In that last pic, after the last rib, her topline has a bump before her croup. That's her lumbar sacral region. If my understanding is correct, it's normally a little further back. It's really nothing to worry about unless you plan to do ride her around hollow backed all her life and not build up any muscle on her. I had a vet scare the snot out of me when he told my OTTB was weak in that area. Four years later and after lot of muscle building, he's a monster and getting comments on his scope and ability to go much further. It's just an observation. That part of her back is weak and subject to pain if not taken care of. Proper saddle fit and good riding is all that's needed to keep it from causing her any pain. With those shoulders and pasterns, I bet she has a wicked nice trot in her. That's the best way to build up that topline, so just use her best traits to build up her worst.
You just have to see your distance...you don't have to like it.