Is it cuckolding if a woman wants to date wife?

They were seeing each other pretty often, but I thought they were just friends. However, one day she forgot her sell phone in the bathroom. I read their conversations and found out they were much more than friends. Then I found some pictures and it was clear that she had an affair with a woman. She is very shy and it was a surprise to me.

Wife has someone interested in dating her so I was curious.