11year old niece i meant 13 sorry typo error

Keeps calling me bandy legs i have a disability it's really hurtful I'm 35 if this was a adult i wouldn't ignore this but she's my niece her saying this nasty word makes me feel really not good i already have low self-esteem trust issues &very self conscious about my problems & how everyone views me. My mum sister have had a good talk to her it's made no difference cos second time she has now said bandy legs it's not a nice word