She was being disrespectful and way out of pocket. You asked her to pick up the plate and I can understand if she misheard considering that we all do at times. She did that on purpose. I do not know her personally and I understand that there are multiple sides to a story, but she comes off as a petty person. She should have just handed the plate to you. Even if you motioned to her it was not disrespectful. I do not think that you have a problem bending down to pick it up, but the situation she created would be disrespecting you.
I do not like people who like to be petty, or get into their emotions. You should talk to her one last times(respectfully and calmly of course)and let her know what's up. If she keeps acting like that then it's best to throw her in the bushes. A person that truly cares for you will not willingly disrespect you even if they do not understand where you are coming from.