ellaYORKIE, I think that jeanm1963 has some really good suggestions!
Usually Petsmart and Petco have puppy lessons and if there aren't any of those available in your area, you might want to ask your vet if he/she knows of local dog trainers. Sometimes the local city community has dog training lessons by an AKC certified individual. I bought a book by the origional 'dog whisperer' and he has a lot of suggestions on how to socialize your dog/puppy in just this situation.
by far the cheapest version is to get your sister,( as jeanm1963 suggested0to bring one dog over for a few minutes or to meet her and one of her dogs on 'nutral' territory,(a park or field, that is not too crowded) so to speak for a few minutes, so neither of them becomes too territorial and have lots of treats to give for good behavior. Walk away from each other if they seem agressive. If possible try to just walk along with your dog next to you and her dog next to her,both on leashes and while watching them from the corner of your eyes, just walk and talk and kind of ignore them but "know" what they are doing while you are walking. Try switching dogs, each walking the other, as long as they get along and don't seem to be too ankcious or jealous
Sorry about my spelling, the spell check keeps telling me that it has checked everything and won't even let me use the thesaurus or lookup options.
