Delta SkyMiles - Question on Standby

My wife's flight from PHX today is at 5:39pm to MSO via SLC.
I am trying to get her on an earlier one.

Expertflyer is showing F3 Y9 B3 for PHX-SLC at 11am and Y6 B3 for SLC-MSO reaching at 5pm. However, the cabin in the first shows full in EC and the second shows 1 'premium' seat available only.

If she tries to take this earlier flight and goes to the airport early, do you think she would get a seat and they bump some people onto FC for PHX-SLC and then would she get this last available seat on SLC-MSO?

Wondering whether it is (1) technically the approach that DL will take and (2) probable that these will still be available by 9am today.

Thanks,

pm

Well, there will be medallion upgrades at the gate for PHX-SLC so that will move 3 people from Y into F.
However, I'm not sure why she would even have to go on standby... with the flights showing any available Y inventory she can get confirmed. There are also seats blocked for airport/gate assignment such as bulkhead that will show as occupied even though they aren't. If the flight is at 11am, then call at 8am to so a SDC. I'd even try calling now and see if the DM agent can help you.

Traveler's elite status isn't mentioned. If she isn't Gold or higher she can't do Standby. If she is Gold or higher, SDC is free, and, as rylan notes, available if Y1 inventory is shown at time of call.