No, don't shoe her longer on the front to bring the front end up. That would cause more problems than it solves. She may just be destined to be downhill all her life. BUT, she is a very long way from the worst I have ever seen. The angle of her back is pretty steep but her withers are really not THAT much different from her hips. It will help to fill in her back once she starts getting rode more often. Worst case scenario, you may have to get a custom made saddle to fit her. I honestly don't believe that it will cause any long term problems.
That is awesome how you got her. You ended up with one heck of a horse. All the Impressive horses I have ever been around ended up having the most amazing personality under saddle.
If you wanted to show her, you could put wedges on her front feet and leave her barefoot on the back end. That would help bring her front end up a little bit. I think that you got a great buy and will really have a good time with her, especially at Open Shows.
I think she's beautiful! Everything I see has already been said. My friend's horse is a bit butt high, but she's a great little mare! It's weird going from my 16.3, even QH to her 14.2, butt-high mare! You really have to sit back, or you go forward! I have a bad habit of perching and on her, I got really off-balanced when posting. But if she evens out, she should be great! If not, just sit back when you ride!
I don't like how downhill she is; at 4 she probably won't be growing "up" so much as she will be filling out.
Her small feet will\may predispose her to conditions like Navicular and possibly laminitis, so keeping excess weight off of her will be extremely important, in keeping her healthy and comfortable in the long run.
She also seems rather uncomfortable, or tense, as she really has her tail clamped...did something spook her by chance?
She's pretty good looking. The only things that jump out at me are her downhill build and small feet. Which are trademark for today's halter horses. Otherwise, she's got a really nice hip and shoulder, and I like her head. :)