I personally think you are way off base. I would be perfectly happy with her as a friend however, she spent 4 months actively making sure I didn't know she wasn't single. Her actions to me are not representative of someone who is single, and she knew that I was interested in her. Therefore, it is not my fault to interpret her actions to mean that she was also a) single and b) at least a little interested in me.
If you were to go down any of those "signs she's into you" lists, this girl checks the majority of the boxes with a few exceptions. Obviously, those are internet lists and very generic, but the sentiment remains true.