Hi Lens, depends a little on your wife's skills/style of sailing. The Jag is a "slalom/freerace board" - so you need a certain skill level and need to be used to using straps further out on the rail. Gybes are more tricky than on the Blast obviously, as the board is wider in the tail. But top end speed and planing quite a bit better, due to the 5cm centre width advantage.
If all of those things are ok, then go for the Jag (if you can test one first, even better). The Jag works great with both S Pace and E Pace, as the cutouts are quite small and the rocker line is lower - means it does not fly away when sails get a lot of back hand power.
My wife and daughter sail the Blast 115, paired with Hero 5.3´s, works great. The Blasts are pretty narrow boards, so a bit more volume is quite helpful. Just not sure how windy your location is? the Gap between Jag 125 and Blast 100 is too big yes - 75cm vs 62cm width, that's a lot.