If the neighbour has built something which is your land the property, that is trespass and you are allowed to make the neighbour remove the trespass. If the neighbour simply ignores your protestations, you have no alternative but to threaten court action to make the neighbour remove the trespass and to make good any damage. Often, a solicitors letter will do the trick without the need for going to court.
Check your house insurance to see if you have legal expenses would pay for the cost of this and if you do have, pass it over to your insurer to deal with.
It may be that her parents did this but that doesn’t mean that she does not now have to resolve the issue.
If however this was done more than 20 years ago, the neighbour can claim an easement to keep whatever trespass is there, in place.
If you could attach a photograph with some explanatory notes, I may be able to advise you further.
Can I clarify anything else for you?
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