What is the ruling on a mother giving all her possessions to her son only, to the exclusion of her daughter, justifying this by saying that the daughter had already taken her share previously? And what is the legitimate Islamic solution for distributing this inheritance?

Islamic law commanded justice among children and forbade favoritism among them in giving gifts. The preponderant opinion according to us is that justice is obligatory among children, and it is achieved by giving the male the same as the female. The mother is like the father in the obligation of being just among children. Therefore, the mother must equalize between her son and her daughter in giving gifts. This equalization is achieved by taking back what she gave to the son or by gifting the daughter a similar amount. If the daughter has taken some money from her mother and has not returned it, then the mother may appraise what the daughter has taken and deduct its value from her gift to achieve justice between them.