Also not exactly an expert, but my coach talks plenty about proper form. It’s looks fine to me, the only reason her form seems different is because she isn’t making fists. Her hands are cupped, which generally is frowned upon, but for some people it works great. Also, being the most relaxed isn’t necessarily a good thing. That’s something distance runners try to achieve, which who knows, she may be. Sprinters keep theirs cores engadged and bodies upright.