I do believe there are reasons for her lack of interest at the moment, but even directly asking her about it doesn't help the question "what?" become more clear.

I agree - I don't see how a committed and healthy relationship could stay committed and healthy if a third party were involved. The only path I see a third party sexual partner leading toward is that of jealousy and eventually a storm of negative emotion for all three parties involved.

At this point, i'm still stumped as to why she would even suggest this as a realistic option - seriously, she wasn't kidding around.

I want to be able to discuss this with her, but I don't want to come off as pushy on the issue. She just says she doesn't know why she has this lack of sex drive, it's just there and theres nothing else to be said. However, from my point of view - sex is a pretty integral part of most any committed romantic relationship - definitely not the glue that binds the relationship but still important from my view. If there is a problem - there has to be a solution.

Is it possible that she doesn't see her low sex drive as a problem? Maybe it's not a problem and i'm just a nympho.

Am I putting too much emphasis on sex?