It's kind of hard to tell from the video, but it looked like the coach was placing her into a square position while the teammates provided support to help her keep her shoulders up. Didn't look like they were forcing her down. But obviously shouldn't have been done if she wasn't ready for it, either mentally or physically.
This reads as if you don't think that video is that bad really. That in itself is very upsetting to me. Alongside the fact that her teammates were laughing as they held her in place while she was clearly in such pain. I'm not upset with them per se - but upset that they have been taught to accept this as normal behaviour. I have a 12 year old daughter and there is no way she could do this to a friend whatever she though of her coach.
It sounds like there are videos from other angles where you can see the coach pushing down on her which definitely should not be done. In the video I saw, it looked like a stretch that could be appropriate if done correctly and respectfully. But my point was that regardless of whether the stretch is intrinsically dangerous, in this case it's clearly inappropriate because the girl is so obviously not OK with it. Coaches need to know and respect their students' limits. And in general, as people, we shouldn't ever be touching someone else against their consent.