groomsman gets a girlfriend 1 month before the wedding

hi all! my fiancé and I are a little over 1 month out from our wedding! we sent invitations out back in february and our RSVP due date is quickly approaching. one of my fiancé’s groomsman just texted him and says he has a girlfriend now and was asking if she’s able to come to the rehearsal dinner & wedding. we’re having a head table with our wedding party + SOs and close family. this groomsman would be flying out for the wedding, so I would hate to not invite her and make him travel alone, but there’s literally no room at the head table unless I make major adjustments. I have also already ordered the name cards for the head table ($20 in shipping alone). what should I do?