To defend Ruto... don't forget that all her bratty moments were when she was, like, 10. Of course she was a brat. You can see in the brief moments we see her as an adult that she's changed since then, if only just a little. Letting Link go, even if it turns out to be harder for her than expected. She really did respect and love him after what he'd done for her inside Jabu-Jabu, even if that's only the love of a bratty pre-teen that she may have held onto through the years.
She's not terrible. She's just a kid.