couplers is spot on.
Why complicate things. Work through the ideas and actions of her with another woman or women, see how that feels, let her enjoy, support her.
Then let it organically grow or not.
If it was me, I'd want to hear all about her encounters, whatever she wanted to share, but no more, no pressure. Over time she may entertain other fantasies built on her experiences with another woman AND how you support and respect her.
Have fun, sounds delicious.