This is a very good reason. But it cannot be the only reason. This is why the Bible says a husband and wife are to become one flesh. Not, parents and children become one flesh. Children are supposed to leave the nest and what's gonna happen to these two once Anya leaves the nest herself? If husband and wife see no reason in each other to cast aside their undying, unreasoning hatred and hostility, they're just gonna go RIGHT back again to fighting and killing one another. This, ladies and gentlemen, is what you call the Bad Ending! Anya cannot be the only reason. She MUST not be the only reason!