As stated above. Ask her if she can get a doctors note. call the medallion desk, move her to your flight, give her your seat in F.
If you don't get the answer you hope for the first time, your best bet is to call 3 or 4 times as YMMV with agents.
This is the time when you need a direct line to Chilsom. @deltaassist might be another option if you are good with 140 characters.
Safe travels, my prayers are with your friend
Maps