
When I got my male mastiff pup, my current dog was nearly 14 yrs old (castrated male). The old dog was not impressed atall about having a puppy around, he even started to refuse to eat. For the first 2 weeks pup spent most of his time in the kitchen, only being allowed out of there on a lead, this helped stop the older dog being overwhelmed by the pup, (it also helped with the cat getting used to the pup & also helped with lead training :) ). After then the pup was allowed out of the kitchen without the lead, but only ever with supervision to start with, as the old dog got more used to the pup they even started t oplay together. I can't remember the time scale, but the pup soon merged in to the point of only being shut in the kitchen if i was going out this progressed to having free-run of the house (not upstairs - he doesn't 'do' stairs) with the old dog.
The old dog has completely accepted the pup as part of the family, due to his age he really isn't interested in playing now though so I always keep an eye out to make sure he gets the peacefull life he's after.
I thought my old dog would have loved the pup from the start as when friends/family have brought thier dogs/pups over he has loved to play with them. I think it was more of a case of him gettting his nose pushed out of joint with a
permentant pup as a pup visiting for play time would have been his idea of a good time.
Make sure your older dog has somewhere she can escape to if she wants to get away from pup, but give them time, she will get used to pup.