Actually, the paladin still has to be LG (that's where the rules are broken...my cohort is lawful, i'm chaotic. DM's reasoning...she's a knight of an order sworn to serve Sune's clergy anyway, and Sune's clergy are mostly CG (and Sune's High Priestess MUST be CG.) So it would be a contradiction if a ruby rose knight couldn't be a cohort to a heartwarder.
(And yes, they're lesbian. LGBTitP unite!)