I agree, it's hard to tell from those pictures, but based on what I'm seeing, she looks fine.
My general rule is if you can feel the ribs but you can't see them, then they're at a good weight. If you can see the ribs, they need more weight; if you can't feel them, they need to lose a few! That's just me though-- not sure if it's the right way to do it, but it's worked for me!
I fret, too, as I just took my horses off my mom's property for the first time when I moved out. I'm a nervous wreck making sure that they have everything they need and that they're taken care of!! You'll be fine-- just keep loving and taking care of them, and keep coming here to ask questions! There are so many knowledgeable people here that are willing to answer any questions you (or I) have!!