Brenda's Flirtatiousness

A related irritant in our marriage has been Brenda's flirtatiousness. This has become a very great annoyance. I have spoken to her about it, and I can see she has tried to control it. However, she apparently needs lots of attention from people of both sexes although I confess I don't feel the same when Brenda's flirting with a woman. Somehow it gets to me more if it's a man.
Do I blow up? No. Do I hound and nag her about it? No.
I know that women rely on making their boyfriends and husbands feel a little pang of jealousy now and again and think this is such a good thing... However, I feel that I lose a little bit of love for her everytime Brenda does this. 
I feel it shows disrespect to me. I've told her: she can flirt all she wants outside my presence... 
It goes without saying this flirtatiousness is another problem between us.