She said she did not want Thomas fired but merely to be sent to another house.
Thomas said she had "had her knees knocked out from underneath her" when she found out about the complaint.
She denied making the comments about the painting, saying instead the person had been "triggered" while talking with her sister on the phone.
Colleagues interviewed by the charity were mostly positive about Thomas but said she sometimes made inappropriate jokes that could be seen as nasty or "devaluing" by those in care.
One colleague said: "Helen can be perceived by others as disrespectful, gruff, overpowering when communicating with staff and service users at times."
Thomas found her workmates' comments "devastating" but the ERA said the charity acted correctly by interviewing them.
The charity decided not to discipline Thomas but to give her coaching to improve her communication and the way she was seen by users.
Thomas believed she was being formally disciplined but that was her own mistake, not the employer's, the ERA found.
During the investigation Thomas was moved to another facility, which her employer said was not a punishment but to make sure she was "safe in the workplace".
Thomas found the move embarrassing but the ERA decided this was not the employer's fault.
ERA member David Appleton found that Thomas had not suffered unjustifiable disadvantages and denied her reparations.