Lae'zel is from a creche meaining she is still a literal child. Take her to the Githyanki patroll where shes trying to convince herself the kithrack was some traitor and not a proper loyal gith. She's on her first step on the path to deprigramming.
I think so, too. In my first game, I had been annoyed by her behaviour, but when I had her in my party, and interacted more with her, I started to feel sorry for her. She had been intdoctrinated her whole life, that Githyanki are superior to everyone else, and she has no experiences at all outside her own society. She blindly believes everything that she has been told (for example the "purification") - and I'm very curious what she will do now, when she starts to realize that she has been lied to. I think that, just like with every other companion, her story could easily take very different paths. (It was quite surprising and very nice to see a softer side of her in the short romance scenes in the PFH, too.)
The way she talks about her dream of becoming a kith'rak and riding her own red dragon, at every opportunity and with great enthusiasm, really made me think of a teenager, I think she is indeed a very young adult.
