Hi 'triber' -- I have actually had an almost identical situation occur when I had a parcel (non-tracked) going right to the middle of the worst hit area of New Jersey during Hurricane Sandy. Unfortunately there was no clear indication the Hurricane was coming when I mailed it, so I just had to wait and see.
The area in which my buyer lived was devastated and flooded out. She told me later she had been evacuated, and that her local P.O. was still standing, but flooded. The parcel apparently got re-routed to a safer location. I found this out because when she contacted me once things settled down, to say the parcel hand't arrived, I suggested she contact her local P.O. to see what they had done with mail for that area. I offered to send another, identical item or refund if the parcel didn't show up at the end of 5 weeks.
Sure enough, the item did get delivered (to her door) about 1 month after I'd mailed it from here. So I'd suggest doing exactly what you've done and then wait -- I'm sure your buyer will have bigger problems on her mind at the moment anyway, and hopefully your parcel will find its way to her when things settle down. At least it's tracked, which means you'll hopefully see when it's in transit again.
If your buyer does contact you if the item hasn't arrived once things are more or less back to normal, I'd suggest asking her to check with the nearest P.O. in her area to see how the USPS was handling parcels during the flood.
Neither snow nor sleet nor rain nor hail... I think it must still apply to the U.S. Mail service (at least it did in my situation).
