Can I Ask My Friend to Stop Inviting Her Girlfriend to Our Hangouts?

A bisexual woman asks whether she can tell her lesbian friend to stop bringing her girlfriend to their hangouts so the two can have one-on-one time, and also raises a double-standard concern about partners. The advice columnist says she should simply speak up, ideally by stating upfront when making plans that she wants partnerless friend time, and only raise the double standard if the friend pushes back.