Sera's views on the Dalish are harsh but not unfounded. Yet, after the events of the Temple of Mythal, Sera just seems downright insensitive towards them. In fact, just as the Dalish look down on City Elves, Sera looks down on the Dalish with almost the same amount of arrogance and insensitivity which is intensified after the Mythal quest and the aftermath of the Solas romance.
She doesn't seem to accept that with the revelation that the Ancient Elves were brought down by their own arrogance (again, keeping true to the Dragon Age recurring theme of how pride can be the downfall of a civilization), the Dalish can finally stop being so arrogant and start moving on from their past. Instead, she's content with making fun of a people who have endured humiliation and defeat countless times.
A Dalish Inquisitor could feel offended by Sera's insensitivity towards her kind and way of life. Sera wanted to help the common folk because they were the ones to treat her fairly first and will always defend them. Yet, she gets upset when a Dalish Inquisitor is trying to help their own people as well as defending them, not being considerate enough to think "Hey, the Dalish may be jerks but they are the Inquisitor's family so maybe I should be a little nicer?". Nope, she retains her prejudiced views on the Dalish.
That's the thing about prejudice. Even the most noble of souls could be brought down by their own prejudice views. This attributes to Sera's hypocritical nature. That she herself can also be as arrogant as Briala regardless of her good intentions.