Are there nettles up at the moment, where you live? There are none showing yet here in Wiltshire. If it was a bit later in the year I'd be agreeing and saying yes, nettles, with no hesitation - but I'd be surprised if that was what it is, at the moment.
Could it be that someone has been spraying the paths or undergrowth with something and it is irritating her pads? That might be why spraying her paws helped.