IMO she comes off as a naive bubbly teen girl. While that IS extremely annoying in itself, it's part of her "growing up" and being "cultivated" into being a good ruler. If you start out as a hero, there's really no room to grow. This expansion sets up the story for the new arc. Of course new characters, especially ones that may grow to become great allies later on, are going to be annoying and cringe. I absolutely hated Nanamo when she was first introduced. Couldn't stand any of the 3 major cities' main characters. They were all cringe and annoying, especially Kan-E-Senna and they were even worse in 1.0. BUT over the course of the story their characters (mostly) grew into decent and likable.
So yeah just think of Lamat as an annoying, naive, teenage girl that hasn't had life kick her in the teeth yet and that leaves a lot of hope for future growth