Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
Has full Title been given to the Council by the Land Registry?
So it would appear that in fact there was originally a mistake at the Land Registry and that mistake has now been corrected?
Your friend cannot be prosecuted for what she did prior to the Council first contacting her.
Equally it is unlikely that she could be taken to court for putting the fencing up at a time when the Council had not yet proved ownership if the land.
However they can now insist that she removes the fencing and if she fails to do so then she can indeed be taken to court for the criminal offence of trespass.
Please ask if you need further details
You are most welcome
If your friend does wish to take the matter forward then she would have to challenge the actions of the Land Registry - likely to be an expensive and possibly futile endeavour I am afraid