Well the barbed wire scars on her rump concern me but not so much as the barbed wire fence behind her....(i know she's not on your property).
Overall she's pretty cute. Rather high withered with a low neck set for an Arabian, and somewhat steep shoulder though hard to tell as she's not standing for this picture. I'd be curious to see what she'd look like in more work, as her hind end is definitely lacking. Decent pasterns, but the length of her hind cannons is what really concerns me as they are almost as long as her upper leg - which does put her slightly downhill as well as more likely to be heavy on the fore. Again it's very hard to tell much from this picture, but I'd say if your friend is just doing barrels for fun, that's fine, otherwise pass. With her hind end she's going to lack the power to really make the tight, compact turns necessary to be competitive at more than just the local levels, and even there it will be a challenge for her. I'd prefer to see lower set hocks with shorter cannons and a broader hind end on a barrel horse.