She said she isn't very outgoing and wants to get more comfortable with you, so it's not surprising that she hasn't initiated much contact with you. Give it one last shot with the group thing, and if she is still as hesitant to go on a real date with just you, then maybe call it quits. It could mean that you two simply aren't compatible, even if she does have qualities that you find attractive. For now, just go with the flow and try to be excited to see her again, if it goes well, hopefully something will come of it.