The best option for Mary would likely be A: Talk to the co-workers and tell them what they are saying is mean.
Addressing the behavior directly can help create a more respectful and positive work environment. However, it’s important for Mary to approach the situation diplomatically and express her concerns in a constructive manner.
If the behavior continues or if Mary feels uncomfortable addressing it directly, she might consider option B: Talk to her boss and let him deal with them. This could escalate the matter appropriately without putting her in an awkward position.
Option C: Tell the co-worker what they were talking about may lead to unnecessary drama or conflict, potentially putting Mary in the middle of a situation she doesn't want to be involved in.
Ultimately, the best course of action depends on the specific dynamics at play and Mary's comfort level.