I think we humans make matters worse sometimes and if you just let the two dogs interact without all your fear they will probable surprise you. I bet Secret would love a puppy playmate.
Why not ask your friend if you can try them together for a week and see how it goes? With mine I was very worried about introducing Bambi, and at first Barley tried to carry her around in his mouth, but I told him no and now they all play together like she's always been here. You have to post pictures if you get the new pup too
