Is a mother who breastfeeds her 22-month-old daughter after weaning her sinful, and is the daughter's longing to breastfeed caused by jealousy over the arrival of a new baby?

There is no harm in breastfeeding the girl after weaning her if she has not completed two years, especially if no harm results from it to the mother, the child, or the fetus. As for the reason for the girl's desire to breastfeed due to jealousy, the reliable source for this is to consult specialized doctors and psychological specialists.