Why on earth are you allowing her to spend so much time on her Ipad? She needs to rejoin the real world. No way would I get her a phone and I would limit her tech time to a couple of hours a day. She really needs to start some after school activities and do some chores around the house. She isn't going to have a clue how to function as an adult when the time comes.
YTJ!!! This wasn't just a party. This was a once in a lifetime event to celebrate your son and his wife. By leaving, you basically told them that you don't care about either one of them and that you just can't be bothered. Actions speak louder than words. I hope they got the message and cut you out of their lives for good.