What happens when someone turns off Facebook chat?

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I have been speaking to my friend on fb a lot recently and sometimes she replies, but she is very busy most of the time. However, tonight she liked a friends page and added someone as a friend. During that whole time, the phone icon next to her name hadn't changed, not even the time since she was last online. I really hope she isn't blocking me as I get along with her really well and I have a crush on her. One of my other friends has her on FB as well but has never talked to her on it. He clicked on message icon and the phone icon appeared.
Could it be a simple case that she doesn't want to talk to anyone right now?
Could it be that she is blocking me, since I send her a lot of messages?
Can she still read my messages even if she happened to mute me on FB chat?

I hope this doesn't sound creepy. I really like her and get along with her well.