回複：急問父母延期問題？？？

1. Normally it takes about 2 months.
2. Once the application reaches USCIS, she can legally stay until receiving decision from USCIS.
3. If application documents are sufficient and reasons are "reasonable", usually USCIS will approve.
4. You mom can go back and come back again, if her visa is valid. The benefit is she may be able to stay for up to a year (if she applies for the extension when she comes back again). But you need to debate if it is fair for your mom according to her health and the long journey.