Gosh even more confused now!! I am just worried that they won't gel, I couldn't bear to have to give the puppy back or to someone else. Like I said its like coco is human if a dog comes around her she will just move on, she has only snapped a couple of times if they have sniffed her too long. I was hoping with it being a baby she might tolerate her more?? Confused 
There's just no way of knowing beforehand. If you decide to go ahead I think it's more likely that they will get on than not get on, although it may take time, and pretty unlikely that it would be so bad that you'd have to rehome the puppy. It happens, but it's rare.
As you can see from the comments above most dogs will at least learn to be tolerant of each other and many will become best buddies.
Good luck with your decision.