What is a complicated friendship? Also what is going on? Read the description.?

So I have a friend, we were ex lovers. She is now in a relationship with someone else. We haven't met yet after we ended up being friends, but we had been chatting a lot.

Sometimes in between she will just come and start telling me stuffs like she doesn't know why did she even loved me. And I would always tell I did love her. She would also say stuffs like she still has feelings for me, but she would never date me at all. But then we would end up changing topic and start talking about something else and all.

Recently I just randomly started talking to her about porn and then she was like she began to watch porn and started telling me that she was in mood. Remember that she is still in a relationship, she decided to talk about what she would have done if we were in a relationship, then I just told her that since she is in a mood I would try helping her out in sex chat. And she ended up doing.

You might be wondering why she isn't chatting with her boyfriend instead, well that idiot isn't giving her time to chat. He is always busy, she says that the last time she even chatted with him properly was 3 to 4 weeks ago. He is always busy going out with friends and all that.

After she was done doing herself, we were just chatting and she wanted to help me out as well, but I kept telling her not to. Later I just randomly asked her what we were, she ended up saying that we are in a complicated friendship. I just said yes as if I understood, but I really didn't know what she meant.