If I bought a round-trip ticket with two names on it, is it OK if one of the passengers doesn't use the return leg?

Right, so I booked tickets for my wife and I round trip. I suppose it’s two tickets, but it’s one e-booking. I want to know if it’s OK if we both use the first leg, and only she uses the return leg, is that allowed? I.E. I don’t want to return with her (haha, it’s just for a week).