NTA, your family doesn't get to have a say in who you're involved with romantically unless they're warning you away from someone unhealthy or abusive. If you two were just making out all through the wedding then she has a right to be a little annoyed at you, but given what you've described, you did nothing wrong.
Not sure you really need to say anything to your sister about it, because honestly no one will validate her view that you were being a dick. Just treat her normally and act confused if she tries to dredge it up.
If / when you get married be sure to specify that she can bring a +1 or date anyone she wants if she's single when that happens.