In your boss’ office, explain that your co-worker seems to be wasting company time on the phone. (unless you work in a call center). Does her job entail a lot of phone work?
Don’t do it in the open.
The problem with that is, is that then we will both be restricted and I have to work with it so it would cause too much friction. We have to get along, only 2 of this in our department. Layoffs are happening all the time here, and i don’t want to look like a trouble maker or seem like I don’t get along with the witch.