That is hilarious! But also really cool, in a sadistic kinda way. Did she know you played tennis and wanted to test your skills, or did she not know, and wanted to show you what she could do?
I had a similar experience. Years ago, when I was enjoying a severance package that gave me 2.5 months off with full pay and benefits (basically a paid vacation,) I started frequenting a bar near my apartment. I was shooting a lot of pool, and flirting with a bar tender who worked there. One night, she finally asked me out, but wanted to go to another bar, y'know, not the one she worked at. We did, and she challenged me to a game of pool since she noticed I played all the time. I puffed my chest out, craned my neck to gain another inch or two of height over her, and accepted her challenge. She didn't completely smoke me, but I DEFINITELY lost, and I was trying my best after a turn or two when I realized she didn't need me to take it easy. What's worse, is I noticed she played left-handed; everything else she did right-handed. I asked after my ass-whooping, and she said her grandfather taught her to play when she was a kid, and HE was left-handed, so she just happened to learn to play pool left-handed. Not only was she better than me, she was better with her non-dominant hand.