In a way, it would make sense, given how proud Lae'zel is. Basically, she's saying without saying that she knows little more about the Astral Plane than the PC asking her about it. Since she's never been there, as she would have been raised on the Material Plane, and not be allowed to join her people on the Astral until she's proven herself. Presently, she isn't 'worthy' of going there, at least by her people's standards, it must grate on her pride, especially given the circumstances she finds herself in.
The fact of her "unworthiness" is sort of confirmed when she encounters the Githyanki Patrol at the destroyed bridge. They clearly don't respect her and are as quick to try and kill her as the rest of the party.
