My mother paid for a "granny flat" to be built onto our house but we have now fallen out and want to sell our house. Would my mother be able to stop the sale and does she have any rights?

Some years ago we gave my mother permission to build a "granny flat" onto our house so that she could be closer to us. We had built our house ourselves some years earlier but could not afford to pay for the building of the flat so my mother said she would pay for it. At the time I didn't take any legal advice regarding my mother's entitlement as I didn't foresee the need as family relationships were good. However, two years ago an incident occurred in the family and my mother is now no longer on speaking terms with us. This is putting a lot of stress on us and we want to move, but we don't know legally if my mother can stop us from selling our house. Can you advise me as to whether she would have any legal claim to stop us? Her name was never put on the Deeds and all the bills relating to the flat are paid by us as the owners. We would be prepared to reimburse her for the cost of building the flat.