A family moves into a castle in Ireland or Scotland and strang things start to happen. Their little girls seems to be haunted by a ghost. The end up finding a little girls body hidden inside a wall. I think it was filmed in the 80's or 90's but not sure. Any help would be awesome it's driving me crazy

This is a guess:

Little Ghost (1997)
From IMDb review:
This lightweight children's movie takes place in Romania, where a young boy unhappily moves to an ancient castle with his mother and no-good stepfather, who plan to open a health spa there. Trouble is, the place is haunted, and the cute little ghost that the boy befriends has her own reasons for not wanting her home disturbed.


Little Ghost (1997) - IMDb

EDIT: Since it is a boy, not a girl, involved with the ghost, I've probably made an incorrect suggestion.

This one has a boy and a girl meeting a ghost girl, but it's set in America: Child of Glass (1978 TV movie).