I have noticed that women in committed relationships seem to flirt more and it's probably because they feel more worthy or they are more confident. I do not know if that makes sexism justifiable... as that's not my field of expertise. Though I do wonder if a post like this is aimed to inflame or initiate a debate?
I flirt because it is fun, but I do tell my SO about it, rather than try to hide it. I also do not encourage or dissuade him from flirting either. Though I tend to flirt less now that I am in a relationship... whereas before I may have been actively seeking via flirting. Now it is just for fun with no real intent.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen