Kellio - It's most likely weather related. Her plane probably didn't make it into PHL because of the snow storms hitting the east coast. Hundreds of flights in NYC, PHL, and New England have been cancelled.
The cancellations cause a domino effect throughout the airlines systems.
There is another storm that will be hitting the East tomorrow which will further
gum up the works.
I would get your mom on any flight you can, because it is only going to get worse.
Bruce