I'm pretty sure there's more to that conversation than just those 3 lines, as I always was fond of it. I believe Gale has an extra question that follows, but it makes perfect sense what she is saying.
The Astral Plane is a place in which time is drastically slowed down, which is why Githyanki cannot be born there and need to be laid outside of the Astral Plane in order to grow which are called creches. It's also the realm of the Gihtyanki. Since they're a highly intelligent race of warriors with a strict hierarchy where strength is respected and followed, a Githyanki has to earn their right to return to their homeworld by accomplishing a worthy feat. Such as killing a Mindflayer which is their sworn mortal enemy.
So what she says fits perfectly, as she is describing her homeworld and that she cannot return to it. Any person that actually pays attention to the story would know this, because this is all explained in the game through idle conversations and direct conversations with Lae'zel.
