She is your mother. She has always been overprotective and didn't have to let you do your own things but still spent her time with you, having learned a lot of things through the years

When your father and mother divorced they shared custody of you having had spend time between the two but after a few months she got more cold and cold until she just straight up refused to let you in and thereafter she just disappeared

Five years later, you were invited with your dad to a dinner at your grandparents' place, and when you arrived, you saw your mother with a man and a little kid and your dad at your side just as confused as you are.

She keeps ignoring you and your dad only paying attention to her new family.