How do you stop one number from getting a 1:1 text in addition to the group text?

[Gmaof3sweeties]

I was trying to work when I got a group text about a family member who was very ill. Someone else in the group (who I didn't have in my phone) kept a running bunch of questions and all I could see was the phone number it was coming from. I texted the group, asking the number to directly text the original sender. Now that person gets a 1:1 text from me anytime I answer a group text with her in it. How can I get it to stop that?