ah, tricky situation
anything brought up re: this subject, any way of approach will end up offending her. do you notice her doing her laundry? did the odor become obvious now that she's wearing sweaters? or does she use those 'balls' don't know what they're called but they're huge in europe to keep somekind of bugs away from clothes. those balls go in the dresser around clothes, and are used year round but mainly used for knit stuff, wool etc.
my mom used to use those and man they smelled bad. no washing made the smell go away. not even dry cleaning.
as a european i'd tell you i'd be offended if something like this were to be brought up. i had an american (meeting for first time) who asked me if i shaved because he had heard frenchwomen don't shave. hahaha funny, considering i am not french but also because i thought it was inappropriate to be asked such a question.
i'd weight in what's more important? her being good with your kids or her smelling good? this topic will make her feel uneasy and always on guard when around you which may lead to her not doing a great job anymore.
ps danish (nordic people in general not just danish) are known to be very educated, very 'clean' well-kept etc.
just my 2 cents