It had to be horrible for your MIL to be so far away from home and family on that horrid day!
It was pretty scary for all of us. We also had a VERY close friend who lived and worked very near the Trade Center towers. Thank God she was OK.
MIL didn't have a cell phone over there, but we faxed her. They didn't know what would happen to the rest of their tour, but they flew home on time, that next Sunday. She was totally amazed at all the security, obviously. We were sure glad to see her when she got back!