Did I cheat on my girlfriend when a stranger flashed her boobs to me online?

A stranger I met through Chatroulette flashed me her boobs after I asked her to. As soon as she started to flash me, I realized it was wrong, and immediately Xed out of the conversation. I love my girlfriend, and would never mean to hurt her, or what I deem actually cheat on her. I know some people consider this cheating on her, but as I feel really guilty and know this is wrong, I never plan on doing something as silly and stupid as this again. I didn't even know this person's name, where they were from, or will ever see them online again. I think it was just a one time mistake. I need advice on not just whether you consider this cheating, but also whether I should realize it was a one time mistake and get over it now, or continue to beat myself up over doing something like this when I can't change what I did. Thanks.