She looks like she has the potential to be a very nice horse but is not fully developed yet. She looks pretty butt high and gangly still. Is she a young two or coming three? Still looks like a baby to me.
I wouldnt risk even that if I were you. Give her until she's about 38 months old and re-evaluate her then to see if she's caught up wth herself by then. At this point she's so butt high that theres no way she can be balanced enough to carry a rider properly and the only thing you'll be doing is teaching her to dump all of her weight onto her front and drag you along for the ride.
Some horses are ready to ride lightly as long two year olds, many are not. I'd say that she's one that isn't. If you do have someone riding her though, make sure that its only at a walk. Anything more than that and you're likely to have a horse with a bowed tendon or torn ligament before she turns four. If she were mind I probably wouldnt even start her until she was atleast three and a half because she appears to be one of the 'late bloomers' and also sems to have the prospect of being a very nice horse...if given time.
We have only been walking her, I have a trainer who has been helping me with her. We are mainly doing ground work and getting her to show more respect and have more ground manners, we only get on her twice a week for maybe 30 minutes at a time.