When my daughter turned 12 – she herself realilzed that now she is Mechuyav in mitzvos and made sure to be more careful.
She now makes sure to daven each day (hasn’t missed one yet), is more careful in her tzniyus (gave up bobby socks) and is in general more in tune with her obligations. She is also trying to be more stringent in Kibud Av V’Aim and Bain Adam L’Chaveiro. She constantly tells me ‘now that I am Bas Mitzva’ I have to do this. My husband is a firm believer in not pushing the kids to do things until they are ready – and he is 100% right. Some children need more time to mature and understand the mitzvos. But once she hit 12 – she was mature enough to take on more obligations B”H. We made a Bas Mitzva in her school with the only men in attendance her father and grandfather (no brothers were allowed as per school rules). Her class and girl relatives attended. She gave a D’Var Torah and spoke about her namesake and her obligations. There was dancing, great food, and a lot of healthy fun. It was truly a beautful milestone in her life.