My guess, without knowing the case, would be that he was brandishing the weapon and making the direct threats, making her "just" an accessory to the crime therefore lesser charge and sentence.
Legal rulings usually take into account the role one serves in a crime, so e.g. in case of a bank robbery, the "just driver" won't get as harsh a sentence as the others, as the driver usually doesn't waltz into the bank demanding the money, therefore those charges don't directly apply.
A polite guest who brings their own refreshments.