Game forcing name change after world transfer, but no existing char with that name ex

Hi all.
So I and my gf have world transferred, and upon landing in our destination realm, she has been advised that she needs to change her char name.

She is unable to use her name at all

However, after looking at the Lodestone, there are no characters with that same name, so there should be no reason why she can't use it.

We checked this prior to us both moving and we would not have moved if we had any cause to believe it wouldn't allow her to have her name. (yes there was the message prior to transfer). But I also received the same message and on landing in new server, no name change was required so we assumed it was a bug.

I hope you can help!