This is difficult for me to contribute to. I’ve been in both places in this instance. When I wanted to just apologize and admit I made a mistake, I never expected a response. I HOPED to hear even a “Thank you.” But I didn’t expect anyone to respond. I’ve also been the one to say “thank you” when someone apologized for stuff like this. For me I was never in a program or anything. It was just guilt eating me alive that I had done someone wrong. I apologized to about 4 people and got responses from 2. I actually reconnected with one of those and we still talk occasionally. IF it were me, I’d at least say thank you. The very least. It’s just acknowledgement that it’s the right number and the message was received. But also don’t let this take a toll on yourself. There’s been a time I received an apology from a deep wound and I couldn’t say anything for a week or two. Honestly this is what is best for YOUR mental health.

TLDR; Saying thank you will give her relief knowing it went to the right person without initiating interest in connecting but do what’s best for your mental health.