The biggest issue is that the artist invented most of those muscles under the left shoulder blade. The ribcage is also a little too tall, and a tad too wide at the bottom.
This reminds me of all those renaissance artists who used male models for EVERYONE, including women and children. The results were confusing, to say the least.
There are quite a few anatomy flaws here, but just because she's supposed to be "muscular" doesn't mean she doesn't have any curves. She's not a body builder, her build should be more athletic if anything. Slightly narrower shoulders and wider hips would help fix the issue of her looking like a man.