Also, you are working 60-80 hour weeks while you pursue your residency, and your wife feels like you should do more around the house??? WTH ?????
It sounds like either:
a) The two of you were never on the same page as to what was going to be expected while you pursued your medical degree; or
b) Your wife is doing the classic "re-writing of marital history" that is prevalent in nearly all affairs.
WAS she on-board with the arrangement before she met this co-worker? Did the two of you discuss and agree upon what each of your roles were going to be and what your career plans and marital plans were going to be?