"You are so obvious! Stop coming on to him. He is not that into you! " ("stop hitting on him", in US Eng ) This sounds a little like a jealous girl criticising another girl. There is no direct synonym for "flirt" which is not at least mildly pejorative ; it is the behaviour that is being socially sanctioned, and the word chosen can't make it OK. By criticising the person - calling her "a something", rather than saying that she is "doing something", you also risk making it a little bit of an insult. And maybe that is what you want. This feels a little like one of those English irregular verbs : "I am being friendly, You are flirting outrageously, She is an utter tart. " Synonyms from online dictionary : Explore 'flirt' in the dictionary 1 (verb) in the sense of chat up He's flirting with all the women. Synonyms chat up, lead on (informal), dally with, make advances to, make eyes at, coquette 2 (verb) in the sense of toy with My mother used to flirt with nationalism. Synonyms toy with, consider, entertain, play with, dabble in, trifle with, give a thought to, expose yourself to (noun) in the sense of tease She's a born flirt. Synonyms tease, philanderer, coquette, heart-breaker, wanton, trifler)

Normally I'd suggest "tease", but where I am it always suggests that you are encouraging them but you are not serious. "Vamp" would be my suggestion, but it should only be used amongst friends as from anyone else it would be considered pejorative. But 'vamp' does carry the essential meaning quite well what you are saying in your example - that she is overly encouraging.

You could use the word "tease" in place of flirt. It has a similar meaning but can also imply that the person is "leading them on" or giving them 'false hopes.'

wow~thank you so much for your explanation in detail~that really helps! thank you

In Germany, we call somebody whos in your words a "flirt" just "player" "womannizer" or less used "playboy" for men. For woman there is no such word in our country which isn´t insulting the person. But from what I found on the web you can also call them "player"