This was also my experience selling in the private Gumtree market. You get questions asking for specifics and you answer them and then they just disappear. Why even bother asking? Between that and the insulting lowball offers, I decided not to bother with it anymore. It was such an awful few weeks I spent dealing with arseholes. I'm not interested in making that my lifestyle. If I were you, I would let it go. You are dealing with someone who lacks the mental capacity to understand what she did wrong. She is not going to react to rant because you will run into the same wall. You might as well explain it to a dog. You will only waste more of your time and get more frustrated because I think you know you will only get more silence in return or an indignant reply about how you are rude because she didn't grasp it at all. You made the sale and that's what you intended to do. If you had to deal with one irritating moron, that's a fair price.