You should wear a mask at work if nothing more than to ease your anxiety and the anxeities of your co-workers. And it's just the "right thing" to do, besides.
I read awhile back that the first Omicron is as infectious as measles and can be contracted from a positive person who is 14 feet away and that Omicron variants are more transmissible Not sure if that is still the thought or how long it takes to get infected. This is 5 months old but there must be more current analysis available. https://www.yahoo.com/lifestyle/most-people-omicron-way-experts-124513554.html
I have an unmasked wedding invitation and reception invitation to respond to in 2 weeks. I feel like telling them it is unsafe and they are just caught up in current trends to pretend the risk is small. My triple vax doesn't guarantee anything.
I don't think you can make your mother wear a mask, even though she loves you and wouldn't want to make you sick. It's not extremely likely she will get Covid if the conversation was brief, even if the person was positive. There is also some science that says people on asthma medications tend not to get Covid as much as average people. What you can do, if she is being casual about exposure in general, is wear a mask around your mother. While you can't control another person's actions, you can control your own.