Vicarious happiness is the irreducible symptom of love. It is automatic, universal, and itself real happiness. Or else it’s not real love.
So when she’s happy and I’m not, I do not love her. And vice versa.
I’ve argued this case with several people without convincing them: there is only one kind of love. There isn’t sexual love and parental love and filial love and patriotic love and selfish love and selfless love. Those are not kinds of love. To the extent they’re genuine and not imposters for something else, they are love mixed with other ingredients, varieties of fear, varieties of advantage, varieties of pleasure, varieties of custom. But the love (again, if real) in each is the same: vicarious happiness is love’s surest sign and singular boon.