Gaslighting at work can ruin your confidence and career. I have seen it.
The behaviour is easier to manage if there are other people in the office who see what is going on. It is much more difficult when one person is singled out by the gaslighter, who is friendly with everyone else. This is when the line between bullying and gaslighting can become blurred.
Over time, this behaviour wears down the recipient, makes them question their skills and capabilities at work and can deeply affect their self-esteem. It is not sustainable long term.
Following the steps above should help to protect you from gaslighting at work. If nothing changes you will need to ask yourself if staying in this job is worth it. It seems unfair to have to leave a job when you are not the one in the wrong, but your mental health and wellbeing deserves to be protected.
Remember that family of origin dynamics will often play out in the workplace. There may be the bully dad or the irritating little sister archetypes to be dealt with. This is normal as the psyche tries to work out the unresolved family of origin dynamics. What is NOT okay is bullying and targeted GASLIGHTING.