Minecraft game data and Family Sharing

My daughter has been a part of my family sharing group for a few years. One of the apps she uses is Minecraft. She has invested many hours into building up a few worlds on her iPad with the app (which I purchased under my apple ID and shared with her).

Now I would like her to start owning her apple ID a bit more, and paying for her own purchases now that she is 16. So, she left the family group, and set up her own payment method for purchases. The problem is she no longer has access to the Minecraft app. The option is for her to buy her own copy of the app, but her concern is that she will lose all her saved games/worlds if she purchases it herself. Does anyone know if this is the case?

For now we have re-instated her in family sharing, and eventually got the app working again (after some helpful advice from other threads - she had to offload the app and reload it again in Settings), but the ideal would be for her to have her own copy of the app.

I haven't been able to find any advice regarding saved games, etc. when leaving family sharing. You would think this would be a common question as kids leave the family sharing group...?