If she put the 2 cycle oil into the crankcase, the engine would not sputter, probably wouldn't know the difference for a year. If she put it into the gas tank, then it would sputter and not run. It would have to be flushed with carb cleaner and fresh gas, ran for a little while, then more fresh gas...
Sounds as if when you changed the oil back to motor oil, you might have tipped the mower on it's side, the gas overflowed the float and flooded the motor. That, you would need to just take the spark plug out, pull the cord a couple of times to get the excess gas out, maybe carb clean the plug and replace it. Should run fine.
Don't be too hard on the wife, as I'm impressed that she even tried to do that. That's cool and the mower can be fixed easier than a marriage.

Try to flush the reservoir, and clean the carb out. clean the boot for the spark plug as well, the clip inside may have gotten fouled.