Did I deserve it? How to make it better?

Today we (Me Male and my girlfriend) were at a friends house to watch the world cup. We were 10-15 or so and we were gonna sit on a mattress and then my girlfriend made a remark about the mattress being saggy. This random dude whos a distant friend then said:"Not as saggy as your boobs", and he started laughing. I also cracked a laugh, I wasn't taking it seriously.

My girlfriend got angry, and wanted me to beat up the guy. When I laughed and said she needed to relax, she called me a wimp then kneed me in the balls very hard. She then said something like the world cup is the perfect chance to kick balls and hopefully my saggy sack will enjoy the pain.

Then she just left, I was really hurting and she left with the car so I had to walk like 5 miles to get home cuz my other friends were drunk. That shit hurt as hell, I had the icepack on during the whole walk home.

I don't know why she was so serious, she's made me sleep on the couch now in our apartment and she said I should never let any man disrespect her body. I thought it was a joke he was making nothing more...

Help me, was I wrong and how to make it better? I tried to go talking to her but she was still angry and had her foot ready to swing at me so I didn't bother.

Did I deserve it? How to make it better?
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