Context: I am a fourth-year graduate student in mathematics at a university in the US.
One of my colleagues in applied mathematics has two advisors, one in mathematics and one in chemistry. He's trying to graduate this semester, and he (understandably) wants to devote the majority of his time to writing his thesis, applying to jobs, etc.
Unfortunately, his chemistry advisor seems to be taking advantage of him. She is continuously asking that he perform all sorts of calculations for her that have nothing to do with his research. These calculations are not particularly difficult, they just happen to be beyond the mathematical capability of his advisor. He suspects that she does not consider them important enough that she would do them herself in the case that she could.
As he still needs her to serve as a reference, he is somewhat limited in how he can handle this situation. His past attempts to refuse or delay working on these "projects" have usually been met with significant resistance. Any suggestions for how he might proceed are much appreciated.