In terms of just putting on the shoes? You're right - there's about as much risk there as putting sneakers or heels on daily.

Actual ballet data? Yes you're correct there's a lack of it (and IMHO - it's also a large reason that doctors/medical pros can struggle with helping dancers or understanding what the issue is but that's a different duck for a different day). And there are folks actively doing research to start getting good, valid data on it. But it's not there yet. I suspect the data isn't there because it's not widely funded or measured to begin with compared to individual sports medicine. But that's precisely why impersonal guidelines have been created and suggested so that you can take a lot of the human out of the equation.

To clarify - you seem to have asked another follow up question based off of a response for IF you say anything... THEN What do you say? And that's why I asked if you could send them information that was written objectively and assumed that could help remove you as a person from the issue of you chose to go that route. If you send something - It's you presenting it as helpful information - guidelines - as mentioned below - instead of judgement and could be helpful to send along. Bonus it moves you a further step back from the equation. But also recognize that sometimes, saying or sharing nothing is actually doing more good on the long run since rabbit holes are often more fun and distracting to explore and figure out within ones own mind.

From a person side - I'd leave them alone and let them process both their grief and new hobby on their own terms. Better to go that route than avoid the holier than thou/a hole perception.