Hi
I am really shy too. You should try talking to strangers over the summer, not the weirdos, but things like making small talk at the grocery store. It just helps in general, to be able to carry on a conversation with any one ( I found this out at job interviews, thankgod for rush.)
don't worry about rush though, the sisters should really be carrying the conversation. It is important to present best self, even if you are a little shy.
also something I find helpful is wearing something special that people will notice, like a locket from parents, new shoes, because it gives you confidence and a possible convo starter.