hey mate,
Look, this looks like evading the inevitable which is: showing this girl you kinda like her. So why dont you invite her yourself? If she accepts, you can just walk up to her and start talking about whatever it is you want to talk.
When you invite her, it doesnt have to mean anything yet. if she asks why, say: 'you look like a cool/interesting person, so i want you in.' Something like that, which shows interest in her, but perhaps not too much interest yet. What do you have to lose when she says no?
Using devious tricks like asking a friend to do your dirty work etc will just make you look for another excuse to not man up. 'What should i do next when she is in that group'? Man up , go to her and talk to her
. What should you talk about? Well, are you interested in her? I bet you are, so talk about her. Who is she? What does she like? What does she dreams of realizing in her life, how was she as a kid? What is the most exciting thing she has ever done? Also, ask yourself these questions so you can answer them when she returns the question
. good luck
ciao