On lepto -- it is fairly widespread across the US (and most places) including city parks etc. Someone here posted a while back about someone with a cavalier in a suburb that got it and died and had only been just on normal street walks. So may be worth checking. Ticks also can be picked up almost anywhere. Our pyrenees used to get them from who knows where when I lived in a California central valley town. So not just rural areas pose a risk. Both might may be worth exploring as a cause.
So glad she is doing so much better!! You must be so relieved.