Using a fictitious name

Dear PAO,

My sister will start at her new job this January 2022. She really wants to have a fresh start because she had bad experiences at her previous work places. As part of her "fresh start," she wants to change her pet name; not her official registered name, but only that which she will be commonly referred to or what we Filipinos normally term as "palayaw." Her friend told her that she might be complained and, worse, imprisoned for using a fictitious name. Can that really happen? My sister is not trying to hide from anyone or do any illegal act. She just basically wants to start anew.