She fully understands the meaning of a potluck. The initial invitation called it a potluck-gaming night, starting at 7:00. In my circle of friends (personal friends; this event is for my friends from work,) if something starts at 7:00, then it's definitely not dinner! However, in HER circle of friends, it usually does mean dinner. I can certainly understand the surprise that it wasn't a dinner party.
Another attendee (AA) was telling me today that she invited the Surprised Girl (SG) to an event starting at 12:00, a while ago. AA sent a note to her invitees to ask if they would prefer a full our lunch, or just nibbles. SG indicated she wanted nibbles. AA and I found it weird that she's fine with nibbles and no lunch, but harped a bit about not having dinner at a 7:00.
But anyway! She's gung-ho for the event now. No other comments were made since I posted this thread. All is well!