Dragonborn - PHB p.32 (Emphasis mine)
Born of dragons, as their name proclaims, the dragonborn walk proudly through a world that greets them with fearful incomprehension. Shaped by draconic gods or the dragons themselves, dragonborn originally hatched from dragon eggs as a unique race, combining the best attributes of dragons and humanoids. Some
dragonborn are faithful servants to true dragons, others form the ranks of soldiers in great wars, and still others find themselves adrift, with no clear calling in life.
Dragonborn basically see Dragons as more pure forms of themselves - as they were created from them, and vice versa, so the Dragon and the Dragonborn are not so different, especially if the Dragon is a priestess.
As for the Paladin, there is too much input to determine the character's reaction - the relationship they have with the other two NPCs, their alignment, their devotion to their god, etc. That being said, as from the excerpt above:
Shaped by draconic gods or the dragons themselves
There's evidence enough to say that the gods revere Dragonborn just as much as Dragons themselves.
But all in all, there are no hard rules in the roleplaying world. They're more... guidelines.