if she starts fucking him and fingering him more and more, all that will make him do is yearn for the REAL thing
When I was with a woman, her using a dildo on me didn't mean I wanted a man--it meant I wanted
her to fuck me very well with it. My boyfriend licking and fingering my cunt (or using a dildo, because we do that to) doesn't make me yearn for women or other dick, it just feels damn good and the connection with my partner makes it incredibly hot.
I suspect the same dynamics are at work for men who are straight and want to experience a tongue, finger, plug, or strap-on with a game lady. If they are straight, they're straight, let's not paint ass play as a gateway activity for those who are sure of their orientation or make sexual curiosity something to be feared. The ass is a universal pleasure zone and there's no reason why anyone should hesitate or fear exploring the area.
Lots of "straight" men realize the advantages of anal play and how it can add so much pleasure to the male prostate. You are lucky that yours' lets you play!
Inded, the OP is extremely lucky. Unfortunately, I have yet to meet one of these men. I mean, I have fingered my guys, but, my Lord, the bitching and clenching involved! :biggrin: