You can’t and shouldn’t force the issue. If it’s not something she’s into or comfortable with then there’s nothing wrong with that.
Is her issue with you and another woman a jealousy thing? You’re going to hear this often, but communication and trust are the key elements to an open relationship. Continue to talk with her about your feelings and wants but don’t be pushy. No always means no. It may not be a permanent no, but simply a no for now. Give her time to get comfortable with the idea and of course continue to communicate with her on how she’s feeling and what emotions she is dealing with. Perhaps one day, she’ll have a change of heart.