AITA for refusing to help with my niece's bullying issue because she has specifically asked for my sister's help?

My younger sister is a school counsellor. She is also a mother of a 12 year old daughter (Bethany). I am the only family members who lives in the same town as my sister. My parents and other siblings have moved to other cities. <br><br>My sister has asked Bethany if she wants to join a school she works at. The school is a bit far from their house and I've heard they've put an application for transfer to a closer one. But as far as I know, Bethany is still going to her current school. Bethany has also asked my sister if she wants to help her with her bullying issue, but my sister has said no. I am very angry with her decision because Bethany is her daughter. Some people have said it's unprofessional for my sister to help Bethany so she can remain a neutral third party but I don't think there's anything wrong with my sister helping Bethany with her bullying issue. In fact, she should have helped her.<br><br>Bethany has now asked me for help. I refused because I am not her mother. If she wants help from an adult in the family, she should have asked her mother. I told her to also not involve our parents in her issue because I don't think it's fair for them to choose an 'eligible' daughter. It's not that Bethany has specifically asked me for help. I would've refused whether she asked me or our parents. It's only fair for Bethany to ask her mother for help.<br><br>AITA for refusing to help Bethany with her bullying issue?