Welcome to the forum and Tillie looks like a very sweet, solid girl!
She looks a little sickle-hocked in back, but that could be the way she is standing. For a pleasure horse, she looks strong and put together well. Her trot will likely not be the nicest thing to sit due to her shoulder, and as others have pointed out her back looks a little long/weak.
Thankfully that's all something that can be mitigated with proper exercise, getting her to engage her hind end and use her abdominal muscles :) If you plan to trail ride with her, you could do work on hills and use other natural obstacles to keep things fun and interesting for you and her.
Again, welcome to the forum and hope to see a lot more of your girl! :)