Suspected Social Security Fraud

hello everyone, to begin i am 24 years old living in new york city. my niece just turned 20 years old and i know she is involved into scamming/ fraud. in all honesty, i keep my distance. in 2020 when i started to work my first retail job, i was paid using paystubs that has my social security number on it. during this time i had my paystub at home, in my bedroom on my dresser. that day my niece came over and she took a picture of my social security number behind my back. i found out that she has my social security number because she was holding it over my head one day. she was laughing because she had my social, i told her to then please delete my information off her phone. i genuinely thought she did, at this time she was approximately 16-17 years old.

in mid november of last year before thanksgiving i made an account with fanduel which is a sports betting app. in order to make an account you would have to put in your basic information such as full name, address and last 4 of your social security number. after you put that information in, a confirmation page comes up with your full social security number to verify your identity.

a week ago i randomly decided to make an account on draft kings, this is also another sports betting app. i had no problem with creating the account but when i put in the last 4 of my social security an error message popped up saying i already have an account with draft kings. i was very confused so i pressed forgot password and my nieces email popped up. i confronted her about this, she is denying this accusation. this is very upsetting because i am older than her by almost 5 years and there is absolutely zero reason as to why her email and phone number is associated with my information.

i am very concerned that my social security number is being used to make accounts that require that information. how can i go about this? from what i’ve heard, her boyfriend participates in a lot of fraudulent activities. what can be done from a legal perspective to protect my social security?