As you say, heavensrun, the new She-ra is powered by love, or in other words by emotional attachment. There's a theme of adora having to "let go" of attachment in order to properly fulfil her duty (see her conversations with Light Hope and Shadow Weaver on the topic). Mara in their final conversation denies that Adora's duty requires her to sacrifice herself and her own desires, and it is through Adora's attachment to catra that her duty is fulfilled. I will concede that this theme could be more clearly shown, but we are explicitly told it.