Hi CAB715,
Just to clarify, did you invite that person in your group message to collaborate on a project? We ask because, if you invite others in your group message to collaborate on a project, those contacts may still have access to the project after you remove them from the group message.
You can find more information about that and how group messaging works here, which may be helpful: Add and remove people in group text messages on your iPhone or iPad
How to remove someone from a group text message
1. Tap the group message that has the contact you want to remove.
2. Tap the group icons at the top of the thread.
3. Tap the gray arrow icon to the right of the contacts, then swipe left over the name of the person you want to remove.
4. Tap Remove, then tap Done.
If you invite others in your group message to collaborate on a project, those contacts may still have access to the project after you remove them from the group message. Apps that host the shared project usually control access.
Want to remove yourself from a group text message? Learn how to mute the notifications from a group text or leave the conversation in the Messages app.
Thanks!