The matron’s office is located just off of the Hospital Wing so that she may easily and quickly service patients.
In HBP19, Harry casts Muffliato on Madam Pomfrey's office so that she will not overhear Kreacher and Dobby fighting.
Harry pointed his wand hastily at the door of Madam Pomfrey's office and muttered, "Muffliato!" so that she would not come running. Then he scrambled to the end of his bed for a better look at what was going on.