I thought AP is needed for her entrance to US next time. Does she need to show AP when she LEAVES US as well?
-Not need, but she need to provide the I-94 to the airlines and thus, USCIS will know she leaves US.
If not, can she just leave and I will mail the AP to her in China once it's approved?
-can not do that. She has to get the AP approval before she leaves.
What's the general guideline for rescheduling appointment? Can it be rescheduled at all?
-Normally you are not allowed to reschedule the interview appointment unless very special situation and need to contact USCIS.
