I think the reason Hera was able to forgive Kronos enough to vent to him about Zeus while having such a distant relationship with Rhea is because Kronos doesn't have any specific hatred for one child over another...
Kronos is willing to hurt all his kids the same in the name of self-preservation (which Hera herself had done at the expense of Hephaestus). There's an understanding there. It's a flaw they both have that Hera has improved from, so maybe her father can too.
It's different with Rhea because Hera knows Rhea is capable of being a good mother, Rhea IS a good mother (to Zeus), so Rhea's failure to be a good mother to Hera is a choice, she chooses not to be a good mother to Hera.
















