In my head-cannon, by Lavellan didn't like how most of the Dalish thought. She wanted to reunite her people (Dalish and City Elves), and saw working, united, for a better future as the best thing they could do.
So when Cassandra asked what it was like living with my clan, I was like, "I hated it." And when Solas asked if he had misjudged the Dalish, I was like, "meh, not really."
My only hesitance with removing my tattoos was a fear of what I'd look like without them.
So, if/when my Lavellan finds out the truth about Solas, she'll keep an open mind towards everything he tells her. And if other Dalish start calling her a traitor so something, she'll be like, "**** you, this is why you don't have nice things"
I removed them, for the reasons above.
I have a similar headcannon. My dalish rogue was in her mid-twenties, and despite her skill with dual blades, was always seen as an outsider in her clan. When Fern Lavallen was a child she gained a scar across her forehead due to an incident with the other children; some of the boys were hunting an orphan wolf cub. She gained her scar by jumping in the way of a club that was meant to strike the cub. Not only did this cause her to be an outsider among the other children, but when she was given her vallaslin, hers did not take on the brownish hue it normally does, but a yellowish tint instead. Thus, Fern became an outsider, often remaining perched by the statue of Fen'Haral, and tending to the saved cub (who would hide in the shadows of the clan, but follow Fern everywhere she went). She was the only one in her clan who would occasionally atop the statue of Fen'Haral with a crown of eflroot or flowers; although her clan preached their lore, she questioned it, and often saw the Dread Wolf as misunderstood, than a trickster. She did not understand why he should be left out in the clan's praise.
Ultimately, my elf was chosen to spy on the conclave for two reasons: 1. because as her Keeper put it, seeing as she was a loner and outsider her entire life, this was her chance to gain pride within her clan and redeem herself. (Though Fern cared more about escaping and exploring than gaining her clan's respect), and 2. seeing as she was an outsider, it would be no great loss should anything happen.
Almost fitting to my canon, in my playthrough, aid to her clan came too late and they were wiped out. Although she was never close, it still struck her to lose her home. Luckily though, upon venturing back to its outpost, she is able to find the orphaned wolf still alive, and he follows her back to Skyhold. (Because if we cannot have mabari hounds, I am giving her an imaginary wolf-pal ... and of course, for obvious reasons).
And yes, she would have Solas remove the vallaslin from her skin. As an attempt to start anew.
(And yes, I know Fern is not the most elven-y sounding name, but that is my usual go-to fiction name
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