whats a good response when someone is nice to u and then rude then nice then rude?

Its a kind of passive aggressive; a nicety followed by an insult. Its a trick to lull you in and once you're in they club you.

The only thing to do is stay away from that person and ignore them. At this point you know they don't like you so what's the point in feeding him/her! If they smile at you, don't smile back, if they say hello, don't say hello back, if they say nice dress, just look at them and not say anything yet carry on with what you were doing. He/She will get the point. You can also just let them know straight up and tell them "save it for someone else!"

its probably better not to respond at all

You could either speak with the person directly to get clarification as to their fluctuating behavior or choose to put your focus elsewhere.

Don't spend time with them.

If its even its fine, it levels out to neither rude nor polite. However if they are rude twice and nice once, that is when you deal with them. PS ignore Jean. He/she is a troll themselves. Tries to make themselves feel better by spraying someone. And is quite feral when challenged

I would probably either confront them directly and ask them why they’re doing it.

stop trolling