Sometimes mothers find it hard to accept that their children are adults. If the child is now a man, then he needs to be respected as a man, and not emasculated and controlled by a woman, even if that woman is his mother. If the child is a woman, the mother needs to understand  that by attempting to micromanage her daughter's life she is actually crippling her emotionally, and this will cause problems either with finding a husband for her daughter, or with her daughter's already existing marriage.  According to the teachings of the Ahl al-Bayt (as), the respect due to parents is conditional upon how they treat their children. It is well known that according to ahadith, it is recommended that after the age of fourteen, the child should be treated as a 'friend', not as a seven-year-old. There is a non confrontational method of establishing boundaries called "grey rock", which you can find out more about on YouTube. You may also want to research "narcissistic" or "controlling" mothers, and something else called "emotional enmeshment". I will update this answer further with references inshaAllah.