I would probably wait until she is near 12 months or seems to be coming out of the adolescence phase 
I think temperment is more important than gender. Has Sadie been around other dogs? If she has, does she take a dominant or submissive role? If she is submissive, than you could probably choose any 2nd doodle, but if she is at all dominant, I would look for either a puppy or a very submissive adult. I have heard that female/female can cause more issues, but i think if both have the right temperments it would work fine
I think temperment is more important than gender. Has Sadie been around other dogs? If she has, does she take a dominant or submissive role? If she is submissive, than you could probably choose any 2nd doodle, but if she is at all dominant, I would look for either a puppy or a very submissive adult. I have heard that female/female can cause more issues, but i think if both have the right temperments it would work fine
