Boxster will be more fun... even with that SHITE gearbox. Alot cheaper to run as well. a 98 will be a 2.5 though and they are pretty slow with that nasty gearbox mate.
Jag much more luxurious and comfy and slightly more practical I suppose although those rear seats are usless and the Boxster has two boots don't forget.
Depends what type of car she wants really.