I need help for my friend

So, my best friend, anatomically female, has the feeling that they are actually male. When I came out to them as Gender neutral this morning, they told me that they thinks they're actually a boy. She didn't want to talk about it in public, so I said I'd text her, but she said she doesn't want to talk about it. They said that they would rather end it than talk. I know that they need to talk about it, so that they actually could think about it, and to find out whether they are a Male or not. Can someone please help me? How do I get them to talk to me? Thanks in advance, Arren