What Do Women Gain From Pegging?

From the guys and girls alike who I've talked to, it seems there's no shortage of women out there who fantasize about 'giving it' to their man. Since women don't exactly derive physical pleasure from it, I can only assume it's more about the mental satisfaction of getting their guy to submit to them and be vulnerable in this way.

This was more or less confirmed to me recently after letting my girlfriend do it to me. She'd talked about it more than a couple times, so thinking it was just some harmless fun, I let her go for it. I came to regret the decision after I found out the dildo she used on me was one of those exact mold replicas of her ex boyfriend's penis.

Maybe in her mind it's no big deal and a dick is just a dick, but I can't help but feel insulted and a bit humiliated. She had to have known I wouldn't like her even having this thing, much less using it on me. Otherwise I feel she'd have mentioned it beforehand. Instead, she conveniently waited till after the fact, and made it a point to ask me how I liked it. Only after I admitted to have enjoyed it did she casually mention that it just "happened" to be a model of her ex's dick.

I'm convinced she took advantage of me purposely here for her own amusement. She claims I'm overreacting, but I know she knows exactly why I'm upset.

Glad she enjoyed it though, cause safe to say I'm not letting that happen again.