Can my mum move to a care home over the border in England if we live in Wales?

We live in Wales but only just, our nearest town is in England and it is about ten minutes up the road. Mum grew up there, her friends and her chapel are there, and it is the place she still talks about when she is confused. Everything she knows is on the English side.

Mum has dementia and she is coming out of hospital soon. We have a best interests meeting next week and I am fairly sure the outcome will be a care home. We have been told she qualifies for full funding, which was a relief, but when we said we wanted somewhere in the English town the social worker hinted it might not be straightforward because our local council is in Wales, and that we could be asked to pay a top up.

Has anyone here ever experienced something like ths? Does the funding follow her, or does living on the wrong side of the boundary really limit where she can go without us paying extra? And what should I be asking in the best interests meeting to keep that option open. Any help really appreciated.