I don’t like my niece get Tiktok?

Anonymous
I have niece from my big sister, because her mom is single mom, i help her to provide her daughter since she was born.

I paid for milk, school. etc
And she is 10 now, and i even put her in the the best Private school in my place, international private school.

But i found out she has Tiktok few days ago, and i told her not to play or get Tiktok or any social media until she is 13.

But her mom defend her, and said how come we forbid her to have tiktok and social media if we are on it, “but we are adult”. That’s what i told her.
Even Tiktok Ceo doesn’t allow his kid to have tiktok, why would we let our kid on tiktok.

I’m upset with how my sister raise her daughter, so i told her if my niece still get tiktok, i wouldn’t pay for her school.

Am i wrong?
Updates
11 d
The phone is her mom’s old phone, coz i bought her mom new iPhone on her birthday last year. I help her coz i feel sorry to her coz she haa to raise her kid alone. And i live abroad, i just found out it when my other siater sent me screenshoot of my niece account. And i told my big sister not to allow my niece to on tiktok and her answer is disappointing. Ans i told my niece is the same, and the last time she just read my text.
I don’t like my niece get Tiktok?
6 Opinion