Esther Ghey is campaigning for tighter restrictions on mobile phone usage for children and teenagers.
She says mobile phone companies should take “more responsibility” to safeguard children online and asks the government to limit their access to social media apps on smartphones.
In an interview with BBC Breakfast, Ms Ghey said Brianna was a “complex” person who loved going on TikTok but says that she was “struggling with her mental health”.
She says a lack of funding for mental health services, means there’s not enough support for people who are struggling.