>>49790494Suwako is a curse god, able to weaken her rivals without doing much directly. The Death Guard can use ailments to crush the opossing army without attacking them directly. She could feel the familiarity there.
Froggy can be very macabre and intimidating when she drops the happy go lucky attitude, and the DG have that gory and crude aesthetic that makes them very menacing
Furthermore, Suwako and their patron god, Nurgle, aren't very unlike to each other. Both are feared for their curses, but also have a softer side, being related to harvests and fertility too. Nurgle also has sided many times with Khorne, the chaos god of war (they are still enemies, its just that they hate each other much less than they hate the other two), which adds another strange paralellism with Suwako siding with Kanako. Also, Nurgle has toad daemons, another connection there
All of these familiarities would make her pick them as their go-to army, I believe