Cannot make a new group chat after contact got an android phone?

Okay, I hope this makes sense. My best friends and I have had a three-person group with all iPhones since at least 2018. We had nick-named the group chat, and have had the same group chat for the entire time, minus the one previous group chat that we had deleted before the long-term group chat.

Anyways, one of my best friends recently got an android. And it will not let us create a new group chat without iMessage, so we (the rest of the group) have been having to turn off our iMessage in our settings every time we want to text in the group. It will not let us delete the old group chat, and every time all three of us have tried to create a brand new group chat with the android phone (same number)—it either pops us as the deleted long-term group chat or the super old one that proceeded the long-term one. I have deleted all group chats on every apple product I have, and it still keeps popping up. And the option to leave the group is greyed out or just not in the group chat settings every time I have tried. This has been going on for weeks, and I have no idea what to do at this point.

Also, I have multiple working group chats with androids. Any help would be super appreciated!