If she's got the lighter colored muzzle and flanks in the winter then yes, she's brown.
Personally, I love a brownskin horse. They are very beautiful, but I've always liked the darker colored horses LOL.
ETA: it's very hard to tell in that pic, it appears that her flank is slightly lighter than the rest of her, but her muzzle isn't. Makes me wonder if she's actually a fading black instead of an Agouti carrier