I’ve always thought the napkin isn’t “lapped” until the place setting is engaged, or is left when signaling you weren’t going to have anything. Similarly, if a side napkin, it went to lap at first contact/use. Then again, I’m no miss manners...
I think the rule is to wait for the host to put his or her napkin on their lap and then you should follow suit. Since there ain’t no others on the table, she’s done messed up.