On the sister/dog front, it's sad if she's being controlled by her husband, into refusing, for no good reason, to let your dog accompany you at their home. However, if your sister isn't in a controlling relationship, the onus is on her.
I have two dogs and over the years, I've entirely understood if they can't stay overnight with me, because of incompatible pets, children, whatever. But you say your dog has met their dogs, which is why you've felt aggrieved.
Resentments can trigger my alcohol seeking wired neuro-circuits in my brain. Nowadays, if I'm not happy with someone's actions, I say so, I've become more assertive. To thine own self be true, is my new motto; within reason and there are exceptions. And your sister's situation and your dog not being welcome, may be one of them. If not, there's nothing wrong with explaining yourself and standing your ground.