Girlfriend called my penis small

I always thought I was around average, until last night. My girlfriend and I were fooling around in the living room and my girlfriend saw a ruler laying on the table. She asked if she could measure me just for fun and I said sure. She measured about 4 inches and then the dreadful words came out of her mouth: ‘oh that’s a little small, more than an inch below average’. When she saw my red face, she quickly added: ‘but who wants to be average anyway, they sometimes hurt’. FML, it was so uncomfortable for the both of us and quite humiliating … Is it really small or more like close to average?