As stated by others, there is no rule that will allow one do SDC exactly 24 h earlier. I do not think that your wife will have a one-stop flight option out of PEK at T-15 to T-23 range, either. PEK-IAD is the last UA flight out of PEK. PEK-ORD and PEK-SFO leave much earlier in the day.
Good luck.