Will the grandmother be sinful if she breastfeeds her granddaughter from her breast, given that she is not a nursing mother and her last childbirth was 14 years ago, and what harm might the fluid in the breast cause to the child?

It is permissible for a woman to drink the milk of another woman. If the legal amount (five known sucklings, and the liquid was milk) is reached, then she becomes her daughter through breastfeeding. However, if the liquid was another fluid besides milk, jurists have differed on this matter. What is stated in the books of the Maliki school is that it does not prohibit, while the Hanafis hold that it assumes the ruling of milk and spreads prohibition. As for the harm of the fluid, one should inquire about it from doctors.