How long should cancer patients who get infection stay off chemotherapy? my mom was off for a month during which her cancer spread. was that too long?

Depends: It depends on the severity of the infection, how the patient feels, and how quickly the counts recover. Also depends on the ultimate goal of therapy and how well the therapy is working or is expected to work. Remember that if a treatment is not meant to cure but rather to extend life, the quality of life is of vital importance and it may make sense to wait. Best wishes to you both.