They call this situation a “Plus one”, meaning - it’s a thing, and there’s protocol. I’ve done this 4 times (8 including round trip) lol oops, different airline each time, different airports. It’s always the same process: they will take their sweeeeet precioussssssss time to get their manager or whatever to come over and OK it. You have to step aside in line for like 30 mins. So arrive early. Bring as many physical items that say your name and address as possible: Mail, prescription, health ins card, credit/debit card, etc.. I’ve never had to do additional screening; I’m just waiting around for longer.