The festival lamps are in her old village next to a destroyed hut, near where you find the ceremonial bowl. I've always taken them. You might not have the option to take them if she isn't with you to explain what they are.
If she's with you and you take them, you get the idea of setting them up (quest "Festival Lights") once you're back at the Temple and leaving the mass/cathedral room. That's when the marker by the pond in the SE corner of WW appears. Might work the same way if you can get them now.
Once the lamps are set up you can ask her out. First time you play a really simple quiz game where she "rewards" you for paying attention if you win. Second and subsequent don't have quizzes, but IIRC she can't reach 5 hearts without at least a second one. Note: after the first one she needs to be horny to accept being asked out.