This claim is misleading because people may think differently on what is "safe". If the claim is that Snapchat's "My AI" isn't safe to the extent that is proposes privacy concerns and potential for physical harm for the teenager, there isn't enough evidence for this. I fact checked this by using an article by Childnet, an online charity site that strives to help children and young people to be safe online. In the article it emphasizes that AI can create loneliness and mental health issues for teenagers as teens can depend on it to heavily for entertainment and emotional support. Overall Snapchats "My AI" is not safe for teenagers in the way it can have a toll on ones mental health, but not unsafe in the way it can physically harm you or put you at risk.
Source: 
https://www.childnet.com/blog/snapchats-new-ai-chatbot-and-its-impact-on-young-people/