It's my Headcannon and I am sticking with it.

I just heard paid more attention on the Imported Dalish Warden content on Dragon age 2 content from Merril’s perspective.

I mean, there are a great number of times that she mentions Mahariel...  But shortly before Zevran's mission, she mentions that: “she thought that she saw Mahariel on the market.” then she says that “even after defeating the Blight she never send a word” Merril wanted to know where her friend was, she wandered for years... 

They grew up together... But Mahariel never writes.

Since Zevran is my LI and husband, my warden went to  Antiva. And after the mention she supposedly spots her clanmate, comes the Zevran Mission. So I think it makes sense that she saw her friend, maybe Mahariel saw her too but hide quickly. 

The Thing is...  I think Mahariel feels like she does not belong in the clan anymore. I think that her life is totally different now. It would be really painful to go back home... and then leave feeling agony in the possibility of never seeing it again.

Merril saw her friend, and her friend saw her. But their paths are no longer connected. 

Maybe the Warden let herself be seen to say goodbye, not just to Merril, but to the innocent simple dalish hunter she used to be.

In the end... She chooses to leave her blood-sister again. And chooses Zevran... She will always choose him.

Just like he chooses her.