The point is every Dalish tribe is not the same and Merrill herself already admitted something. You have nothing to stand on. Just admit she really can be airheaded at times. It's really not that big a deal.
The Dalish in "The Stolen Throne" explicitly state that the Dalish speak entirely in elvish with one another, and Lavellan uses elvish with Mihris, can speak entirely in elvish to Solas, and entirely understands Solas' friend speaking ancient elvish to Solas. Frankly, I don't see how you can say I have nothing to stand on when I repeatedly point out the examples where Lavellan clearly knows elvish, or how it was previously stated that the Dalish speak elvish as their first language in "The Stolen Throne".
Frankly, your condemnation of Merrill is also absurd when you're ignoring her accomplishments with magic and constructing the Eluvian simply to mock her for adjusting to an entirely different culture from her own.