In my humble opinion, there is nothing wrong with your horse's withers. I fear the saddle isn't as high quality as you thought it would be. It kind of looks too narrow for her, which is weird because she doesn't look that wide. It almost looks like it is narrow in the gullet but flares out wide at the bottom of the bars. Just totally the wrong shape for your horse.
I really hate to knock your new saddle, but I can just tell by looking at the leather that it is one of the cheap imports. I had one too and was lucky to sell it. So I wish I had more positive news, but the problem is the saddle, not the horse.
Not that you can't buy a cheap saddle and have it fit. Or an expensive saddle and have it not fit. Price isn't an indicator of fit. It's just when you buy a better saddle you have better odds of it fitting, that's all. And a better resale value if it doesn't fit and you have to sell it.
I've probably been through 6 or more saddles trying to fit my round Mustang, and finally purchased one off of eBay that fits like a glove! But I was buying and selling saddles for several years before I found the perfect one.
So I wish I had the magic answer for you, that could solve your saddle fitting woes, but having been through it myself it is a lot of trial and error and buying and selling several saddles until you find the right one.
What CAN help, is to make a wither tracing of your horse (there are articles on the internet on how to do this) and take it with you saddle shopping OR send it in to a reputable saddle shop and see what they have that they think will be a good fit for your horse. That is not a 100% accurate method either, but it increases your odds. That's finally how I found a good saddle for my Mustang. I found a saddle maker on eBay and sent in the wither tracing and they told me what saddles they had that would be a good fit.
BUT, if you are on a budget, you will be better off getting a good quality, name brand used saddle in your price range. Good saddles hold their value, so if you don't overpay and get a good used saddle, then even if it doesn't fit you can get your money back out of it. I've even come out ahead on a saddle or two doing that.