I don't believe she realizes that she is making herself ridiculous.
"I was at Vinton's last Saturday afternoon.

Jessie Meredith invited another senior and me to luncheon there.

Imagine our surprise when a prim, precise little figure marched up to our table and seated herself as calmly as though she were the president of the senior class.

There is room for four at those tables, you know, and we had not reserved ours.
Still, there were plenty of other tables at which she might have seated herself.

It was rather embarrassing for all of us, but it was worse when she tried to break into the conversation.