Did I give my friend the right advice?

My best friend has been having issues in his relationship with his girlfriend , his girlfriend has been very negative towards him the second him and I started chasing our dream of brewing beer. Which him an I been planning for a long time and his girlfriend was even aware that we were going to do this for a long time , Now that we officially started brewing , his girlfriend has been doing her best to rain on our parade, last night my friend came over and told me his girlfriend and him had a huge fight again and she basically told him that she has been talking to someone else, during the argument. I told him to dump her if she is saying shit like that , I said she is already cheating on the relationship by investing her time into someone else. And whether she is or not , who says that shit in a relationship? What would you do if your partner said that to you during an argument?
Did I give my friend the right advice?
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