Tell your good lady that "A" is usually used as it's the quickest and easiest way of getting a neat job (and therefore the cheapest). "B" and "C" are both possible but are a lot harder to get really neat if there are any discrepancies (read "always"). If you want to go "B" you'l find that unless you put a bit of a "V" groove in the join between the jambs and architrave it will look like crap as there will be discrepancies between the wall and the jambs. If you want to go "C" you'll need to use a square set metal moulding to plaster to and this will give you a raised ridge around the frame. Unless you are (or get) a good plasterer it will look pretty ordinary. The other alternative is a shadow line moulding for the plaster, this will give you a small square recess between the timber and plaster and better hide any discrepancies. If all your other door and window openings have architrave then it would look better IMHO to keep them all the same.
Mick