I think it's more likely the City Elves told Sera she wasn't being elfy enough after she got adopted by a human woman and lived outside the Alienage.
Either way, it couldn't be too similar to what Finn's going through seeing as how some of the clan members are willing to exploit loopholes in their laws to help out another. Even the Thane of the clan often uses loopholes for the benefit of the clan.
Furthermore, Sera's comment about how she has the right to be scared of demons because she never received "special" training like Vivienna and other mages was rather infuriating and retreads the tired out "I'm poor and oppressed so I suffered more" defence that Sera constantly uses. Most mages who go through the Harrowing end up horribly traumatized and potentially even more terrified of demons than before. Its one thing to imagine what a demon could do, its another thing to actually know what a demon is capable of.
The there's her reluctance to accept Sigrud into the Inquisition. Now, Varric's worries actually carry weight as he's seen what a mage fused with a spirit could do and even then, it never made him so horribly prejudiced. Coming from Sera though, its more shallow as it just comes down to her not liking someone because their strange and she can't understand them. Again, retreading her usual fear and hatred of anything magical.
I imagine that Sera would be one of those kids who if she were to hear that one kid in her neighbourhood is a mage, she'd join together with other kids to throw rocks at the mage kid while yelling "Freak!" or "Monster" repeatedly.