Hmmm, I've been thinking about your post, but nothing brilliant is coming to mind...
Has anything changed to make her a bit insecure about being out? Has she been ill? Teething? Anything like that? In the meantime, it seems like a good idea to keep taking her to the moms and tots group since she's comfortable there and likes it. Does she sit on your lap when you go to other things or does she just cry the whole time? If she's really that uncomfortable I think you probably shouldn't take her. Maybe take just a few weeks off and see if that helps her?
Also, I wouldn't worry about her making friends just yet or what other people think. Chances are it's something she needs to work through and when she's got it figured out, she'll be fine.
Sorry to not be more helpful!