This is not even remotely normal - I would be very very worried about an infection setting in, if it hasn't already. And no - the age difference wouldn't cause this. I have adult dogs spayed/neutered regularly, and this is still not normal. Adults will sometimes seem a bit more sore, but nothing to this excess.
I uploaded a photo for you so you can see what it SHOULD look like. Adult females getting spayed at the vet I use (which is not my regular vaccination and basic stuff vet) go in first thing in the AM. They are spayed, then in recovery at the clinic all day, through the night, and I can pick up anytime after noon the following day. This photo was taken of a 1 1/2 - 2 yr old female the afternoon that I returned home with her. So about 30 hours after surgery.
When done by this vet, there is no licking, no scratching, no biting of the incision. Previously it was done by my regular vac. vet, who is supposed to be very good. First of all, they used external means of closing them up (the above photo is all internal!), and many times dogs were having problems afterwards (though never to the extent of leaking excessive fluids like your dog is). So I stopped using them for surgeries, and it's been fine ever since.