She doesn't want to reply to sender. She wants to post a reply in the group. In any case, for all I know that may not work for her either. I doubt Reply to Sender or Reply to Group has anything to do with this. Her email is just not handling a reply link.
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J

Messages are the sole opinion of the author, especially the fishy ones.
My humanity is bound up in yours, for we can only be human together. - Desmond Tutu