We all have our fantasies... but some of us are able to make them happen.
She has hers, but through her beliefs and upbringing - won't likely follow through.
I'd say, come up with more details to help her out... Go to a store and buy a cheap bondage kit to try out... its fine for novice role playing, but shit for long term usage. Here is an example: go to Amazon.com , and do a search on " bondage kit " - do this on a Incognito browser if you are just looking.
You can get a starter set for about $18~35. But I'd recommend the black and red $29 kit. (you get 2 extra pieces compared to the $25 kit). She knows you're not really going to hurt her, etc... so while in fantasy, put the binders on first... maybe. Then the cuffs while you are describing your fantasy.
While she is bond and sucking you off, then use the toy and say "its one of the guys". Do that a few times, and you can start making it real. There are a lot of "conservative" publicly looking people who are kinky fuckers behind doors. Hence my distaste for anyone who is self-righteous.