GrahamK mentions 'MUC' but that is the IATA code for Munich and I got the impression he meant somewhere else.
I would agree that going Biz for a medium distance and then spending more on the hotel will still be a VERY fine treat for the lady. If you are going long haul (HKG etc) then a proper biz class is still such a change from Y that she will be seriously impressed.
I recall the first time I treated a lady to biz, it was with JAL from HNL to NRT and she said that I had ruined her for life as she couldn't face Y again!!