How should we raise our single pup without littermates?

I enjoy your site and the tremendous amount of experience and information you make available to others.

My husband and I have owned German Shepherd dogs for over 20 years and have begun breeding the last five years. My breeding stock are OFA and of good quality and excellent temperament. My 5 year old female has produced 3 litters and just had her fourth. However she developed gestational diabetes. It threw everyone for a loop as it is apparently unheard of in dogs and especially in german shepherds. I happen to believe it has happened more often but owners simply didn't recognize the symptoms which mimic a normal pregnancy (excessive thirst, frequent urination, eating large amounts of food, etc.) I contacted vets and teaching hospitals all over the state and around the country for information and just about nothing is available. We mainly were concerned with the bitch's health as her blood sugar levels were sky high near 500 and with up to 90 units of insulin a day came down to the 400's. All my dogs are highly active walking/running up to 4 miles a day in addition to swimming in our year round creek plus are fed a high quality kibble in addition to some raw. So her fitness really helped her out. She delivered on her due date without complication (no hypoglycemic crashes or cesearian) 4 pups who were all very tiny, 3 were fully formed but tiny and stillborn, the first was tiny but was breathing right away and went to find a nipple. The pup weighed around 8 oz. and we decided that if it could survive on it's own we would let it live. She nursed round the clock with just a little help in the beginning from us but by day 2 no help was needed. The bitch takes excellent care of her and the pup named "Solo" has more than doubled her birth weight in 7 days. All motor functions are normal and the mother is down to less than 20 units of insulin a day and sugar levels dropping daily into the low 300's, so it would appear that just as in humans the diabetes will dissappear on its own after her hormones level out . She will be spayed after weaning. My question is since it would appear this pup is a survivor, how should we procede in raising her without siblings. I know the importance of the social interaction between the pups and we are concerned how "single puppy syndrome" may affect her. Should we seek out similar age pups in the coming weeks for her to play with or is that just too dangerous? Have you had experience raising a single pup? Any advice would be appreciated.

Sincerely,
Karen