Is it obligatory to give the husband's sister a certain amount of money in exchange for her participating in the land lottery on his behalf, given that the husband is the one who paid the price of the land won in the lottery?

Drawing lots is a means of identifying the specific rightful claimant from among a group of claimants. The lot falling on the name of the questioner’s sister-in-law makes her the rightful owner of the land, to the exclusion of her brother. She is permitted to waive her right to it in favor of her brother in exchange for money, or without compensation if she does so willingly.