[Tifa doesn't know Vriska well enough to have a baseline to judge her current emotions on and it's not as if they're meeting for exactly cheerful reasons to start with. So she'll pick up on the somber mood but it doesn't occur to her that it might be from things other than the current ones.

though... she did see Loki's post. Anyone the troll felt close enough to to do that, it has to hurt when they're gone...]

Only in the middle of a fight and that's not flying so much as - well, fighting. [She'll pick her way over.] Is that common where you're from?