I recognized a girl three years younger than me as my mother, and finally learned that she was my cousin's daughter and my niece.

It's nothing. Admit it. Treat her like a mother. I also recognized my female teacher's daughter as a mother. She didn't when no one was around. Later, when the teacher found out, he invited me to dinner. Of course, only when the three of us are together. My names are Mom and Grandma.