All you need is love. Love makes the world go round. Love lifts us up where we belong... Shall we go on? In A Wrinkle in Time, love is the nuclear option (how's that for a pop song?) that conquers all else in its path. Is love blind? Sometimes. But in a world where appearances are so often deceiving, a little blindness can be a good thing. Love can allow a person to see beyond the surfaces, to get at the truth that's lying underneath...and that's the power of love.
Love is a force for good in the novel because it promotes interest in others over self-interest.
Meg's love for her father initially blinds her to reality, and it must change for her to grow up.