Just what is Gimli planning?
How long until this misunderstanding is cleared?
The question is, why did she disrobe in the first place. Was it just for seduction? I think she would know by now that the MC wasn't motivated by that.
We know what her plan is, she mentions it back in chap 11.2 when she talks about the dark elves. The entire tribe of dark elves is cursed, and to break it, they need the demon king's heart, which she now knows means she needs Gaile (though she already suspected it).
Also during that chapter, we see both her + her dark elf subordinate wearing the same outfits she is as she disrobes in this chapter, so it's probably not seduction. It's just her basically revealing her true intentions as a "dark elf", and not "the guild receptionist", since this whole thing is secret + separate from her guild duties.
She also wears the same outfit in 17.2 when she's tailing the group in the cockatrice hunt, so it's probably less like underwear and more like a stealth suit dark elves wear around (or just traditional garb).