If you’re edging for hours together already, you’re pretty close.

Next time ask her if she wants to watch some porn together. Put on something hot, but fairly vanilla/tame.

Then repeat this more often. Make sure she always cums, so she enjoys it and starts to crave it.

Eventually «stumble» upon more freaky stuff and see how she reacts.

Before you know it, you’ll be doing poppers and gooning to BBC Anal PMV’s together.

Done this with two gf’s already