I have a DD 26 month old and are in a similiar situation. I think you can explain the anti-social with G+. If she prefers older children and adults it is not abnormal for her intelligent level. A while back I talked to an expert and this is before discovering the gifted route and without discussing gifted she informed me that socialization will be our hardest challenge for toddlerhood and throughout life. We were not as smart as you to get the kiddo on the waitlist until she was almost 2, so we are still waiting, but in the mean time we have her in dance class which she loves. Maybe you could find a program that meets once or twice a week for at least an hour where the parents are not in the room and see how she does. The interesting thing about our DD is she loves dance, loves her teacher informing me that Miss Sarah is the best teacher I have ever had... okay that is her only teacher, but as for the other little girls in the class doesn't really pay that much attention to them. She is getting better but still not that interested in the other girls.
So maybe by doing some other short program you could get a sense of how she would be in the 5 day program and if it is worth the deposit. It also could be a way to baby step her. And maybe you put her in a 2 or 3 day program for a few months and transition her into the 5 day option.
But in my opinion socialization is still important which ever route you take. Good luck!
