Hi we have Lily 2years and Mia 4 months. They get along just fine, sometimes Lily get's sick of Mia and tells her so but I think that may have more to do with the age difference than a female thing. Plus in this pack I'm the top female LOL and both girls know it
I love having my two ladies and I can put matching bows in their hair
I don't think you can ever guarantee a new dog will fit in perfectly, I think it takes time and a bit of work for everyone to get along well... just like the humans in the house
Good luck... I say pick the pup you have a connection with!
Let us know what you decide