IMHO it's less of a crap move when you stay in the doubles and drop singles, since dropping singles only affects you and not your partner.
Also, I don't know the extent of Saisai's injury. It's possible that with rest and treatment she may feel she can play. Or she may wait until the last minute to scratch in the hope of a miracle recovery.
I know in the juniors I see players (including minimiffed) who are legitimately unable to continue a match in the morning, but by the time their second match rolls around (USTA junior tournaments are usually double elimination) they are good to go. As an official and parent, we/I let the kid play.
(For example, a few months ago, mini miffed had a migraine, had to retire after the first set, went home, took drugs, came back four hours later and won his second match--all kosher under the rules).
I hope she makes the right call and is able to be in good form for the AO.