Can a completely introverted person become an extroverted person?

Is it possible even if it is a bit by bit? Or is this just a character that will remain unchanged regardless of whatever you try?
I met this girl, she says that she prefers sitting alone in an empty class in her school rather than sitting with people, though she wants and tries to be friends with people in her class but there is this one problem that stops her. She can be friends with girls (she gets anxious whenever she thinks of talking to guys so she couldn’t be friends with guys) but her problem is maintaining their friendship. She said she can ask the girl she wants to be friends with about her interests like favorite books, favorite music,... etc. but once she knows all of it she can’t find anything to say in the days after that and she just remains silent during most of the conversations. She wishes to be more talkative and more outgoing but she never finds anything to say to her friends whenever she meets them except about the weather and general stuff..
Maybe she lacks knowledge?? What do you think? How can she be helped?