I have never heard about anyone spitting up gray secretions. Maybe you could ask Karen more about what it looks like, or what the texture is, etc. It may just sound bizarre because of the way she has chosen to label it. It could be from another medical condition related or unrelated to one she already has, and a better description could help you help her. Does she get regular medical care?

Obviously, just because someone has/may have mental health issues doesn't mean they can't be a great friend. WE are all great friends, but it makes me happy to read this:

"I will have to be mindful of my mental health and put up boundaries on this relationship."