I had a dog while growing up that was spayed at age 6 and developed incontinence later.
My old girls in my home now, one of whom was spayed prior to 1st heat (is now 10 1/2yrs.old), have not developed it. The other old girl is 13...not sure when she was spayed.
Keep in mind sex hormone related cancers are quite common in older dogs, we've seen those cancers many rescued dogs who make it to their golden years and are still intact.
Congrats on the new puppy, I'm sure she'll be fine