You have to remain calm. Do not show her that you are upset no matter how upset you really are. Prepare yourself mentally beforehand - think about how you should react when you see her and rehearse that in your mind. Release some of the anger before you see her tonight. Unfortunately, you can't control how she spends her time. She already knows you want to work on your M. Showing her that you're upset will only place more pressure on her and may push her further away. Remain calm, friendly but detached.
Me47 H46 S13 M16 Piecing since May/09
"Life is 10% what happens to us and 90% how we react to it." Lou Holtz