I LIKE my dog reacting to anything/any noise about our doors, and feel that is a security PLUS, and a huge benefit to having a dog. I love him doing that.
but, if you do want to desensitize your dog to never bark at the sound of a key in the door, you could do that, if you truly wanted that.
For the slamming door,
you could get some
high value treats,
bring dog over to door,
and slightly open it so it only barely makes a noise, which he probably wont' react to,
and CLICK/TREAT his nonreaction.
Set Missy up for success, reward her
super quickly, before she has much time to react. Missy will probably begin to figure this out pretty quickly...that she is getting prizes for NOT barking.
Overtime, advance along, so you are now opening the door slightly more, so the door will now make a slightly louder noise as it closes,
and quickly CLICK/TREAT a nonreaction from Missy,
and so on. Slowly rising the criteria she has to be calm about,
slowly, as she develops both the understanding of the wanted behavior,
as well develops the self control to perform the wanted behavior.
Praise her a lot as she is given the treats, too.
Slowly, slowly, increase the noise the door will make when fully slammed. It's okay to sort of preemptively treat Missy, giving treats at the second the door slams, to almost prevent her from being able to bark, cuz her mouth is too full.
For the full on slam, you might have to move her back from door just a bit, and have volunteer slam the door, maybe...?
If that doesnt' work, you could maybe try giving her a yummy kong to chew on, to help distract her while you close the door, and praise her nonreaction, and then, overtime, try the exercises without a kong.
see if that works?