I can give you a little bit of a critique from that photo, but as palominolover said, squared-up pics from all angles (both sides, front and back) will give a much better idea of how she looks.
That being said, here's what I see (starting from the front and working back)...
She's a little bit ewe-necked, but it may just be that her neck is undermuscled. Her throatlatch is nice and clean, and I love her head. Her neck ties into her shoulder/chest pretty well.
Her shoulder is a bit upright, which generally indicates a rougher ride, but this also depends on the horse. It's been said of my gelding that he has a rather upright shoulder and should be a rougher ride, yet he's one of the smoothest-moving horses I've ever ridden.
She's the tiniest bit over at the knee, but nowhere near as bad as some I've seen. She looks like she might be a wee bit tied in behind the knee, but again, nothing major. I like her pasterns and their angle is good. Her knees are set nice and low, which is good.
I like the length of her back. Not too long, but not too short, either. She looks like she might have a wee bit of a hunter's bump, but that might also be just her need of topline muscling. Something about her flank bothers me, but I'm not entirely sure what it is.
Very hard to tell anything about her back legs, other than her hocks seem to be set pretty good and, again like with her front, I like her pasterns and their angle.
Overall, she's a good-looking mare, she just needs a bit more muscle and some definition.