I could write that narrative in this forum:
Physic voice " Do not be afraid, we may seem like the monsters you heard of, but are only attempting to save our race. Dramatic pause ... "You know, We are the most powerful and most feared of all sentients, and soon you will know that power " "When you are ready, reach out and we will begin your training"
Yeah, that works!
Another random thought I had with this set-up was that this might be an interesting moment to introduce the dream person. If the Dream Person is what helps you escape here, it'll go a long way to giving it credibility and listening to it more enticing. Although Larian's sort of done that with Divinity 2 (the original, Dragonknight game).
To make the choice even more ambiguous, you can even add a knowledge check when you meeting Lae'zel (Arcana?) to let you identify her as a Githyanki and their reputation.