About six months ago I began noticing that something wasn't quite right with a coworker (Miriam). She is in a different department but my team works with her on some projects. Issues ranged from emails written so oddly that intentions were unclear to ignoring/violating corporate compliance. Shortly after I noticed the trend, another coworker mentioned similar issues they had with Miriam.

Over the next few months, things got worse. Many times Miriam sent comments or direction either very vague or simply incorrect. In these instances, I would reply for clarifications: "Can I get a few more details?", "Are you sure about this?", "How does that jibe with this other thing that would contradict it?", "Is this a new process?", etc. Sometimes I'd get a response that made sense. Sometimes I just used my best judgment to move forward. Miriam didn't seem to notice either way.

My coworker has a good relationship with Miriam's supervisors (and I do not have a good relationship with those people) and had mentioned to them some of the smaller issues. The response was that Miriam is dealing with a family issue and to cut her some slack.

Many projects that generally run smoothly had problems this year. As 2018 winds down, there have been talks about why certain projects were bogged down. Until last week, I'd only had private conversations with a couple people about Miriam being at the center of it. 

At an event last week, which Miriam was not attending, I spoke up something like "Miriam needs to take a break, handle whatever's distracting her from work, and come back when she can do her job well." This was not received very well by others. AITA for making clear that I want a competent coworker?