Hi S.,
I can so appreciate your desire to have an outside source reinforcing your emphasis on social skills. I have heard of a few in the past, but don't know of any currently. So I don't really have a resource for you but want to encourage you to continue training your daughter on how to behave in various circumstances. At 6, some of it may stick, but so much of it will be learned from your behavior in social situations. When you are thanking your host/hostess for having you over, make sure she is with you, hearing how you say it and how you respond to the others. And then perhaps as you drive home discussing why it is 'good manners' to say thank you, ... showing regard for others, appreciation, etc.
And it is always good to have lots of healthy outlets for the silliness! And perhaps discussing later why it was fun and appropriate to be silly and have fun in that way in that environment and perhaps seeing if she can think of places/times/situations when it would not be appropriate.
Just some random thoughts on the process. My daughter is 8 and I want for her, too, to feel comfortable behaving in an appropriate manner in a variety of situations and to be a blessing to those around her. And to have fun being 8, too!
HTH,
A.