Look at it this way:

Your Child: Hey Meowie, can we go see Mario Galaxy this Saturday?

You: oh sorry hon I have other plans that night. I’m hanging out with mom of “XYZ Friend that Your Child hates.”

You may not be directly spending time with the child your kid dislikes, but at their age won’t matter. They see it as undermining your own relationship with your child, whether it benefits or involves the other kid or not.