Is it normal for my friend to enjoy thinking about emotional pain?

This isn't about me, it's about my best friend. I've been worried about her for a while now and I have no idea how to help her.

I've known her for almost five years now, when I first met her she used to absolutely hate and avoid any kind of pain. Physical, mental or emotional. She didn't want knowing things that hurt her and she avoided getting hurt or even reading books about pain. One of the main reasons she's completely against relationships is because she fears getting hurt.

Lately, however, she started LIKING the idea of pain. Emotional pain. She thinks about the pain death causes and a lot of dark things and she enjoys it. She says it's her happy place. And now she's all about reading books where the characters are in a lot of emotional pain and she's nothing like she used to be before. One time she told me she's afraid she'd start a relationship just so she can get hurt. Granted, she was joking, but I can't help thinking there's a bit of truth behind her words.

I'm not making any of this up, I know it doesn't make much sense but it's how it is. She doesn't talk about this often but when she does it scares me. I'm worried about her and I want her to see a professional, she says she wants to but she's not ready yet. Please tell me if this could be normal and if there was anything in my power to help.