My Moms Office Denied Here Ada Accommodation Twice. Compromise They Proposed Is Clearly Retaliation.

Location: Massachusetts

My mom has works at a large well know business for the past 10+ years, for about 8 of those years she has had cancer.
her position has changed over her employment but overall she’s been happy there.

About a year ago they ask her to cover her position at another local office as her coworker had left and they had yet to fill the position. She did, mostly remotely from her original office which they were fine with. sometimes she would have to go into the other office. she started noticing weird symptoms coming and going And her oncologist suggested keeping a diary of her days to figure out what was happening those days. She figured out it was days she was at the other office. She spoke to coworkers at that office who some reported the same symptoms. Headaches, overall unwell feeling, feeling foggy, and a cough. She did bring this issue to the business and an environmental study was done and black mold was found in the building. Which they swiftly painted over and declared it safe. The suggested remediation from the mold company was not followed and the symptoms continued.

My mom brought this to the company who told her to request an ada accommodation if she had to. So she did providing a letter from her oncologist about the health concerns he had with the mold and her compromised immune system.
They denied the accommodation and told her now her options were to work In the location that was making her sick 30% of her time or quit. She got backup documents from her doctor and letters from other coworkers as well and her request was denied again.

Now being told her position was eliminated so she could now work part time loose all her benefits and insurance or take the of now spending 50% of her time In The office making her sick or leave. she is beside herself I feel like this can’t possibly be legal. what do we do? Has anyone experienced this?

***Thank You****
Thank you for all the great suggestions and links. I’m going to go over them with her tonight. She is terrified to lose her job because that means losing her insurance. which would render her cancer meds and Dr appointments completely unaffordable. I’m hoping I can persuade her to take some action because at this point it seems like she feels like it’s hopeless. I will keep you updated, they gave her till April 13th to make a decision.