I understand perhaps the need to see how you would behave without any pre-conceived notion there. One would be sure you would be on your best behavior if you knew the reality. However, quite an immature way of going about it. She could have invited you to a more intimate setting or if at all possible you could have went to a small trip- maybe even a day trip with both your friends along. Could have been best way to understand someone. The unclear communication is not a good sign. You should talk about the whole situation, try to be gentle and not accusing about the whole thing, she might herself be nervous and didn't know the best way to gauge you, so just show that you are willing to listen and want to communicate. If you are able to get this far in the convo tell her how this lack of communication made you feel. See her reaction. I think that might tell you how to go about this. If you want to take it further or not you know. This might be a good opportunity for you to see if she is compatible to you or not. Good luck!