ND has a animated model only of Tina (revive terminal) on CND main area on Next Island, it is not a real avatar, and doesn't actually heal. It is a bit like a non working npc and is named for her and nicknamed Healer. I saw that, along with a section of the island named after her as well as being his way of replacing the memorial that has been missing on Calypso for so long, and done to his own personal taste. He may or may not want the old Tina statue to return to Calypso now, I have no idea. As for the actual avatar of Tina, it was retired in the past but MS9 saw an avatar on Rocktropia with the name 'Island Girl' and she is in ND's society terminal as well. If MA has allowed this avatar (account) to be active again, obviously we have no idea what the arrangement is for it, or who owns the account now (could be her family for all we know), but I for one have assumed MA is well aware of what accounts are being used and by whom they are owned, so I never suspected that ND or anyone else somehow managed to activate and use an account and avatar without MA's knowledge or permission, unless they hacked into MA's computer system.
Anyway, yes, it is good to see the baby's memorial back in place, for a long time after VU10 there was nothing on the 'new' Memorial Island at all for either of them. Memorial Island was originally created for the Tina memorial, and later a couple who played the game lost an infant and asked to have that added. There was a lot of discussion about possible future additions for others over time. The Tina memorial finally returned, without the statue or plaque either I think, and in some ways I found that even sadder.