Amalia, Ingrid Alexandra, and Elisabeth keep in touch with each other via the app. It makes sense as they are all in the same age group and are all preparing for the same roles in their countries. The three friends can help and support each other. I hope Leonore will some day join the group. I don't think she has met her fellow future Queens, but it would be lovely if she also develops friendships with them.

I think the late Elizabeth II shared a similar friendship with Beatrix and Margrethe. I know they wrote letters to each other.

https://people.com/inside-bond-between-3-future-european-queens-including-whatsapp-group-11986666