Here's a silly problem I can't seem to fix. I have Avios award tickets on a US domestic flight for my family tomorrow. My 13-year-old daughter's reservation is in a separate PNR. US's online check-in system thinks she's an unaccompanied minor and insists that we see an agent to check her in. I've called US (and then re-called!) and have been told there's no way to get the system to realize she's "accompanied" and let us check her in.

Has anyone ever encountered this problem and found a solution (other than arriving early at the airport, and waiting on the ticket counter line to get a boarding pass)?

BTW, I assume there won't be an idiot at the airport who will insist I pay an unaccompanied minor fee when I'm obviously traveling with my daughter.

Thanks for any guidance.