Hey ,I dont assume it is .
What are her hobbies? And why does everyone automatically assume some variation of Autism. Do you guys know how rare that stuff is?
The other people probably dont bother with her because she does shout and bickers and butts into their conversations, perhaps this is the area to help her in, some social" graces, and possibly as you say you are her own source of entertainment she has come to rely on that, maybe time to back off a bit and let her find her own common ground. she is latching on to the adults because that is what she is used to doing being with you. So when she goes to clubs and guides is there a way she can gain more independance an go alone.I understand your concern and care perhaps it needs you to let her make her own way.
Have you had her assessed for asbergers syndrome? What does she enjoy doing?