The show's interest in educating its more liberal viewers on the conservative case for environmentalism (as explained by Deseret News) would and could be admirable, were it not so thoroughly unsubtle, and so obviously tied to the series' need to keep as many viewers as possible (open to) rooting for the Duttons.
Positing Summer as a viable love interest for Costner's character — without giving her any sort of inner world, complexity, dimension, or degree of intelligence about her own beliefs — wouldn't just be contrived and clumsy from a narrative standpoint, it would also serve to further indebt the series to its increasingly right-wing fanbase (via TV Guide). If that's the goal, then maybe "turning up the heat" for the couple while keeping Summer as a trope makes sense. But if Sheridan wants to remain baffled and amused by the accusation that "Yellowstone" is a red-state show, then Summer's return will have to be accompanied by some much stronger character development.
As an actor, Perabo is more than capable of portraying a fully developed human being. What's more, giving her a storyline other than "naive, vegan damsel in distress" could help "Yellowstone" push back against the increasingly warranted critique (see: this Reddit thread, and the she-wolf, sexpot, or victim archetypes that run rampant in the show) that it struggles to imbue its female characters with any degree of depth, realism, or actual strength and agency.
