I'm not so certain, given the map, but I think we need more information before being certain. Perhaps this is where the Inquisition comes in, to play a role in deciding between two human nobles contesting the rule of the throne, or the elven struggle to emancipate themselves?
The Dalish historically blame the Chantry for the fall of their kingdom, they are constantly on the move because of the templars and violent Andrastians, and the elves who submitted to human rule were forced to abandon their gods and convert. I think some of the People would see the Chantry as a nemesis, and I can see Merrill becoming a hero for some of the Dalish by defying the templars at the heart of their seat of power over eastern Thedas.
I simply think it's possible. I'd certain like it if the Dalish Inquisitor could express an opinion on one of the Elvhen who took on the Knight-Commander and her entire templar army, and defied her.
On the first point: I agree, we do need more information. But remember that Orlais armies are all raised and they're fighting in the region the elves want. If the elves indeed rise up... they'll have the fight for their lives.
On the second:
Let me begin with saying that I like Merrill. A lot. I get "little sister"-vibes from her.
Yes... the elves blame the chantry... but they seem to blame humanity as a whole more. The templars are a threat, but not their primary enemy. They hound them, chase them... but I dare say that they see the Chevaliers as the true enemy. In addition, as Arianni points out... they don't seem to hold the Circles in a very high degree of trust.
They blame the Chantry yes... but I'm not sure the Chantry is the true enemy.
But I think Merrill's true obstacle is not whether the opponent was right, though it factors in, but what she did
I am not sure I can ever see Merrill being a hero to the Dalish unless she does something more. Look at what she did: She disobeyed her keeper. She, a first, left her clan behind. She dealt with a demon/wicked spirit. She left the life of the Dalish behind to live in a human city. Think of the symbolism in this. Again: She left the life of the Dalish behind. To live in a human city. What is the difference between a city elf and her in the eyes of the Dalish?
Who's going to believe her side of it? Is she even going to protest any accussation?
I am not trying to say Merrill chose the wrong thing here. I am not trying to say Marethari was blameless. I leave that for other debates. I am strictly looking at what the Dalish will think... and nothing I've ever learnt about the Dalish suggests they'd ever forgive that.
I would be happy to be disproven here. But I think, that to the Dalish, Merrill has become a city elf. Her only saving grace would be if no other clan knows...
Other than that... I think Merrill would have to martyr herself before they accepted her as one of their own again.
And that makes me sad 
Orlais is an Empire in decline. Nevarra, Ferelden, Civil War, Chantry/Templars split, Circles breaking away... and now we add the Elves and Inquisition to the mix.
When Anderfels broke off Orlais in 1:65 the empire halved in size. For all intents and purposes it looked as if Drakon's empire wouldn't survive his sons. 45 years later, the elves had burnt Montsimmard and was besieging Val Royeuax itself.
Then orlais conquered the world...
Don't count them out just yet 