bluflamingo

I agree that first tell your friend that you like her partner, and would welcome the opportunity to get to know her, but that you'd love to have time alone with your friend to talk about things that her partner might not either be interested in, or are part of your shared friendship that might make her feel like an outsider. It's okay to say you felt awkward talking about things that you felt were too personal to talk about in the presence of someone you didn't know, no matter how nice they are.

Then cross your fingers and hope your friend understands!