I actually disagree. B'Elanna wasn't a reset button, she was a work in progress. When one watches episodic tv, one gets the impression that all problems are solved within 60 minutes, including commercial breaks. Childhood trauma revealed, faced, defeated, move on before the previews for the next week.
B'Elanna's traumas were deep and not eased with a simple pat on the back and an "atta girl". She needed to learn over time to trust people, and to trust them in different venues. Sure she trusted Chakotay after serving with him in the alpha quadrant and the delta quadrant, but not enough to share with him her personal story, much less her depression over the dead Maquis.
She didn't confide in Tom during "Faces" because she trusted him, as much as it was because she was scared and vulnerable and he was handy. Sure, she told him about hiding her forehead as a child, but never confided anything else of significance until they started dating 3+ years later.
B'Elanna's journey was similar to many "real life' journeys, one step forward and often 2 steps back or several steps sideways... but she stayed the course and reaped the rewards.
Naturally, YMMV.