Her legs are on the long side, but that's such a common thing in anime art that tagging it as bad_anatomy for that alone seems a little unfair. I don't see any other significant anatomical issues.
The person who tagged this has a history of tagging bad anatomy without explanation on posts without any obvious flaws, so I'm assuming they just didn't like it. Removing the tag for now until someone can provide a good reason why it should be here.