it's funny how metamour relationships seem to feel so much more intimidating/tense/scary/awkward/"insert word for your experience here" more than just random friends/coworkers/etc. I hope that you and her can find a rhythm that feels comfortable and relaxed. It's sounds like you and your husband will work something out so everyone's happy.
I know negotiating certain boundaries governing the interactions of myself and my metamour have been bumbly. The other night, I was in the car with O and A and I was leaving, so I gave O a hug and then there was an awkward pause and O said, You know, you can hug A too. And I was like, I can? (I'm not sure why i was so incredulous).