How do I explain the departure of my beloved hygienist?

I work for a DSO. I have worked with an amazing hygienist since we opened. Not only is my hygienist a great producer, they are a great person who I consider a friend. Patients also love this hygienist and many come to this practice just for them. Unfortunately, our manager has butt heads with this hygienist since the day they started, and the situation has become hostile enough the hygienist has put in their notice. Trust me, I have tried to mend this situation so many times, but it's past fixing. I am beyond frustrated and upset with how things turned out, but I cannot leave this job for the foreseeable future for a variety of reasons.

Moreover, their patients will be passing over to our other hygienist who is more "aggressive"- a lot of them will end up being re-diagnosed as SRPs which means I will have a lot of upset patients to deal with. I'm exhausted just thinking about it. Has anyone dealt with a situation like this? What should I tell my patients when they ask what happened to the hygienist?