I need help. My 11-year-old girl cousin thinks she is my babysitter. She's cute and all and my mom says to play along. It was OK at first but then she wanted to give me a bath! No way i said and now i am so grounded. What can i do?

This is not her but it looks a lot like her. My mom says i shouldn't put her face over the internet.
Reason she thinks she's my babysitter is because i used to walk her to school (i get schooled at home) and then walk her início and i stayed at her house and she was like my tutor cause my mind works mais like a fourthgeader and she was in fifth grade and thinks she smarter and she is but doesn't make her my babysitter still i played along cause i need moms help and Emmy make me sandwiches and leite so one dia when i spilt leite on me she made me take off my camisa and pants and said i need a bath no way am i gonna take off my underwear for her and now i grounded.