Is it possible that she may have fallen while playing and maybe injured her pelvis or SI area? I don't see any swelling in that region, but if she was goofing off and ended up doing the splits with her hind legs she may have strained some muscles and ligaments. I don't think it's wobblers. When she's cantering around she swaps leads just fine and doesn't stumble at all. Other than her hind legs looking very stiff and not wanting to bring them up under her she looks fine.
The way she swings her legs out to the side could also indicate sore stifles. Sometimes when babies are growing their bones grow faster and the muscles and ligaments have to catch up. I can't remember the name of the condition but sometimes you have to watch how much protein they get. What are you feeding her? Many times with that condition once you adjust the diet, after time the condition subsides.
If you don't mind I would like to cross post this video on COTH (chronicle of the horse). There are a ton of knowledgeable people over there and most likely have seen this before.
She's a very nice looking baby by the way...
A good rider rides transition to transition, a great rider rides half-halt to half-halt!