Not to worry, she's carrying just fine.
Mares can carry differently -- and maidens are the trickiest. But to top it off, you have to look at where she has been and what she's been through in this past year.
Now she's on a good diet, getting good hoof care and love, and she's blossoming under your care. Baby's can take a lot from their moms during their growing stages, but only NOW is she getting the nutrition she needed during the prior part of her pregnancy. So while maidens typically carry their babies up high and tight, she didn't really have the muscle tone to do that. So, she's showing us more of a broodmare belly -- which is just fine!!
Baby is moving into the "forward of center" position, and beginning to line up nicely, so I believe that all is going well!! She's going to do just fine, and with the continued good nutrition, she'll get that baby safely on the ground as a healthy and strong baby!!
You might want to read the Katya's thread here -- she's a Grants Pass Auction girl -- and you can see the very positive changes in her from when she was first rescued until now. A perfect example of what good food, love and care can do!!