Would this be illegal/against the law or not?

[Bob]

I got into an argument with some girl i don't know that lives around my area on facebook. I told her if i ever saw her i was going to break her twig neck. I said this because she was calling me a terrible names, and being very mean. I'm not allowed to post the things she was saying because they were too profain. She also continued talking to me,so wouldn't that invalidate her going to the police and saying i "threatened" her or "she felt threatened" Because you are not supposed to,and it wouldn't make sense to, keep talking to someone if you felt threatened.