Yeah, the big one. I can't find it
Obviously, you first need to have met her, you have to reach a certain point in your relationship with her, I also think you need to have a highish lvl (somewhere around 8 or 9 i think)
after that, she can send you a mail to tell you she's on uveto or you can go and talk to bart and ask him where she is or ,by luck, meeting her in the street of uveto (don't remember where exactly, somewhere next to the stadium i think) spilling her drink on her (don't remember if it's actually random or part of the story)
Then again, i'm telling you for this quest because you quoted me, but there is two other "big one" (that i remember), like the "assault on korgii hold" or the quest with the frostwyrm.