I see no logic in the above statement. You gave your kid a smartphone when she was 14. By today's standards, that's very late, and it's basically just one year before Denmark's proposed ban on social media. You can ban your child from having a smartphone for an arbitrary amount of time, but they are a future adult. Adults use smartphones. You can either prepare your child for the potential negatives of smartphone use, or they will learn that through their own experience later. There's no escaping smartphones and social networks.
The only way to deal with this is to talk to your kids, warn them, and educate them. I gave my kids smartphones when they were 8 and 9 years old. Those phones were fully managed by me, and the only web pages they could access were their school pages and Wikipedia. Every year, I relaxed these restrictions and frequently talked to them about the dangers of social media. Now, they have almost fully unrestricted phones, and I don't think there's anything to worry about.
The problem with social media for kids and teens is constant comparison. Any kind of comparison, but predominantly about visual appearance. Most people will never win this fight, and I believe it is a parent's role to explain this to their children. Banning smartphones or social media won't save anyone from facing the reality later on.