Since you decided to write a question about her, I bet you care about her and are concerned. It sounds to me like you don’t think it’s healthy, and you’re uncomfortable with it. Is that true? My guess is that if the Fluther collective deems that this situation is in fact unhealthy, you would just have more righteousness when you have the conversation with her. If you go to try to convince her to get out more and be more healthy, I doubt that would make a difference for her – other than to alienate her from one of her few friends (you). What I think would be more effective is to be very curious with her, about whether it’s working for her! If it is, why would she change? If it’s not, of course you could support her in getting out more and meeting more people. To answer your question, it’s a valid choice that a lot of couples make. Seems to me they are getting most of their needs met through each other, so why would they go out? They may be missing out on things, but if they don’t know or care, that’s the way it is. If they don’t want to change, that leaves you with the choice to accept the situation the way it is, and stay or leave.