Try thinking about it from the supervisors side. Do you have any evidence that she has not tried as hard as she might? If not I think you might owe her an apology.

I wonder if your supervisor might be finding it hard to place you because of your "social awkwardness/being shy and timid" tendencies. You might wish to think about this as she might well bring it up. If she brings it up I trust she will do in a constructive way and offer you help with this. You might also ask her for guidance on how you can help her place you.

I know it may not have been the wisest choice I suspect you might be right that this was not a great gambit (even in America where people seem amazingly "in your face"). Can I suggest that you might have been wiser to say something along the lines of "Can I discuss with you whether I have been unlucky with my placements or whether there is more I should be doing to get the best out of them?"

Just a thought. Good luck with your meeting.