AITA for inviting my friend's ex to our regular running group without telling her first?

Ruth stopped tying her shoes when Drew walked up and said, "You invited him?"

Six friends have been meeting for an easy Saturday run for about a year. I organize the starting time. Drew used to join occasionally when he and Ruth were together. They split four months ago, and he hasn't been since.

He messaged me asking whether he could come this week. I like Drew and said yes. I didn't tell Ruth. Part of that was forgetting to send a message; part was not wanting to ask a question that might become a veto.

Ruth left before we started. Later she said the group was one of the places where she didn't have to think about the breakup, and that seeing him there without warning made it feel as though everyone had already decided she should be fine with it.

Nobody else had been consulted either. I told her I hadn't organized a reunion or asked them to talk, just let a friend run with us. She said knowing he would be there would have let her decide whether to come.

The breakup details are private. Drew says it was sad but straightforward; Ruth hasn't given me a description I can compare with that. I don't want to make membership depend on choosing a side, but I did make her first encounter a surprise. AITA?