1. Call the Elite line yourself for your mother-in-law. Ask them to re-route you on UA through SFO (or ORD). I would say SFO has a better chance. ORD is getting a bad storm tomorrow as well.
Another option = Leave from PHL instead of EWR. As EWR is going to see more CO cancellations.

2. See if you can find availability for one ticket using your miles. Book it (whatever route is available, especially out of west coast).
Call CO and ask them for refund for the original ticket (original flight canceled, you dont want the new itin).