My mum told me she cheated on my dad...

With another woman, who my husband and I happen to work with.

I'm in my thirties and my mum has drunkenly told me that she cheated on my dad when I was a child in the past. I ignored it and just carried on through life.

This weekend she had too much to drink and told me she had sex with one of my colleagues 9 months ago.

Am I a bad person for just wanting to forget all about it and just move on? I have two kids and have enough in my life without adding this BS on top. Am I a bad person for not wanting to tell my dad and not wanting any drama?