Tween girls! Gotta love'em.
My daughter is 19, so we survived the age!
I think there are a few ways to handle this: (and I've done all I will state at varying times):
Have limited treats in the house, in the cupboards (I don't like this one, because, it's not healthy food and some if it is just too tempting)
Have treats that I am not interested in, in the cupboards (still not healthy, and still not my choice)
Buy the treats, (1 per week) but child must keep it in their bedroom (back to the healthy thing)
Have no treats in the house, but allot a "treat allowance" for when they are out with their friends (and I would NOT ask, what it was spent on)
I am now at the point where only healthy things come into the house. My daughter can fund her own junk food, if she wishes to eat it, but I won't buy it.
You are not a mean mom, you are working to keep yourself and your family healthy.
I'm sorry your daughter has taken this public. Social media came on the scene without an instruction manual
You will figure out something that works for your family.