Sale of property

A property was picked up in 2003 in Bangalore. Later on it was gifted to a daughter who stays abroad. She had given a GPA to her mother to sell the property. There was no construction on the property. Owner of the adjacent site, now claims that the survey number given to her site is incorrect and that most of that site falls under their survey number. Now one person has come forward to buy that property. He is asking for a GPA so as to enable him to negotiate with the adjacent site owner. One of clause in the GPA drafted by the gentleman who wants to pick up the property says "generally to do all acts, deeds or things what so ever which in the opinion of my said attorney ought to be done, executed and performed in relation to any property or in or about my concerns, engagements and business as freely and effectively in all respects as myself could do the same as if I were personally present". In case this GPA is not given, the buyer may back out and the possibility of the adjacent site owner usurping this site is very high. Kindly advice.