Hi!
What it says on the subject -- Lae'zel will not follow the party in toggle mode UNLESS she's the active character. She will just stand there while the rest of the characters move along.
This started in the Nautiloid, after clearing the first room with devilkin, right after meeting her, but has been going on well into the Druid's Grove. It's very annoying, but I'm not sure that it's a bug -- is this a "feature" of her personality (she refuses to be "led" anywhere?).