I don't know much about the Dixieland saddles but if you think one will work, give it a shot.
A horse's back can change throughout their lives, depending on how they are being ridden and what type of riding/work they are doing. The saddle may have fit her when you first started riding but the more you rode, the more different muscles built up in her back and made the well-fitting saddle not fit so well anymore.
One of the reasons why I suggested a saddle fitter is that you may not need a whole new saddle, the fit might be close enough that you would just need one of those special saddle pads with the removable shims and the fitter would be able to tell you if you needed one, what brand is the best, and which shims you would need to leave in or take out. They aren't terribly cheap, but when compared with a custom saddle, they are much more affordable.