I can't give you a definitive answer, but I'd like to make an observation. You say you've always been perfectly happy to be alone and it never palls, but according to your own post, you got married; you are married. Sure, people, particularly people in unhappy marriages, often claim to be "alone" and/or "lonely" even when their partner is in the same room. (And I don't mean your marriage is unhappy, but of course some marriages are). But the fact remains that they really aren't alone (although they can be lonely). But they aren't alone. If you think you can't help your wife with her loneliness and you have intellectually dusted your hands of her emotional state because you can't wrap your head around what loneliness is, you could ask her what you can do to help her with her loneliness. I don't believe we have to understand everything about someone to help them, particularly if we are open to the idea of asking how we may help.