The current fic I'm reading has got me thinking a bit about how Velanna and Elenaria would rub each other wrongly, even though Velanna becomes a Warden.
One thing is true of Velanna, and that is she is obsessed with Elven Rights - namely Dalish Rights to the point of being almost as scornful of "Flat-ears" and she is of "shemlens" (humans). I had an idea that some time after coming to Vigil's Keep she gets wind of Elenaria's stone (the Silmaril that is Elenaria's true form, Elennárë) being some sort of Elven artifact and starts prodding at Elenaria about it.
Of course, as you can imagine, Elenaria is very protective of her stoneform - she was separated from it for anywhere between 10-13 years in the Circle Tower (taken off her by Irving after the failed Tranquility attempts) and only after it was returned (again, Irving returned it) did she understand the half-life she had been living in that time - with the memory block that had been put on her she only really remembered her life in the Tower and couldn't remember the full extent of her past - memories that her true soul retained and she got access to once she was holding it again.
One thing about Elenaria, she doesn't even view herself as truly elvhen, even before regaining her memories. She doesn't even think herself a City Elf because she was raised in the Circle, which is a culture all to itself, and from the Blight onwards she's a Grey Warden and now remembers her silmaril history. And Velanna picks that up pretty quickly and thinks of her as some sort of traitor to Elven rights for it, and therefore not worthy to possess any sort of elven artifact.
So that's where they end up clashing - Elenaria has an "elven artifact" and Velanna thinks she is unworthy and that she (Velanna) needs to take it and study it for the sake of "worthy" elves.
I can currently imagine Velanna starting out just trying to wheedle info out of Elenaria as to the silmaril's nature and how she found it, but Elenaria refuses to say much. Actually, how Elenaria came to have it is not much of a secret - Elennárë has been living with the Surana line for centuries and Elenaria is the first child of Ethiliel, Elennárë's last bearer (not to mention that Elenaria is Elennárë's remote-control body). Velanna's smug Dalish superiority likely makes her think that it is a crime that a line of City Elves have kept something so valuable, especially a flat-ear who panders to shemlen (Elenaria).
So Velanna tries to steal the stone, planning to up and leave once she has it, work out how to draw it's power (she has seen Elenaria use White Fire and thinks somehow she can tap into that), but while Elennárë cannot function directly through the stone while bonded to her elven body (under normal circumstances Elennárë can roll herself around, communicate via telepathy and use magic to interact with the world) she can still sense when people touch her stoneform, identify them and sense their intent and general character. So as Velanna tries to pick her up, Elennárë reacts and burns her, while Elenaria comes running and there's a huge argument about Velanna trying to steal the silmaril and Velanna being her usual superior Dalish self. I can see Elenaria telling Velanna that if she is willing to steal Elven artifacts from the Elves who have owned them for centuries, then she is copying the exact actions she hates humans for.
And in the end, Elenaria probably doesn't ever explain the nature of the Silmaril to her anyway - doing something like what Velanna has just tried would permanently make Elenaria distrust her as yet another thief, like Melkor. She certainly would avoid mention of the other two, currently residing in Denerim in the possession of the "shemlen" Queen (this incident might happen while Anora is still pregnant with the twins).
An incident like this probably would result in severe punishment though - maybe Velanna is put in the dungeon and is still there when the dual attack happens and manages to escape in the confusion. I do know one of the epilogue results say she has a stone fall on her but no body is fond afterwards, and another result has her eventually leave anyway, running off into the Deep Roads to find her sister.
Reading: The Keening Blade (fanfic)