That would seem to be the best option. DL won’t cancel the reservation (assuming she checked in) until ~T-15m, at which point I can’t imagine they’re going to want to be playing musical chairs to boot the OP back to coach.

But I guess worst case, if the system does flag the unaccompanied companion for downgrade they’ll probably just swap him with the next elite on the standby list which would likely mean at least a C+ seat.