My divorced friend Michelle is mad at me because her boyfriends' kids got together with my kids. Was I wrong?

Since my kids wanted to see Michelle's kids during a weekend she didn't have them, she was upset with me. However, the kids had fun getting together & ended up staying at our house overnight. Told the kids to ask their mom's permission first but they couldn't reach her on her cellphone. So we called their dad (Michelle's boyfriend) which infuriated Michelle because she said I disturbed them during their weekend together. She did not speak or email me for three months! Finally, after I sent her a gift basket to her work, she called to thank me. Her reasoning behind the anger was, "What if you were divorced & I took your kids out?" However, these kids were not HER kids; they were her boyfriend's! Although we talk now, we are no longer as close. I'd like to know your opinion.