Id think she was more brave if she stuck around for a few days before running off to NY.
She needs to take some responsibility for this, not just leave it to the OP, he parents, the groom and his parents.
She needs to let people know in some way, thank them for their time and money in coming, but sorry, for personal reasons she cant go ahead. However she will help people who have taken time and money to support her wedding, to recoup some of their costs - returning any gifts, helping sorting out with any hotel cancellations, etc. And of course it costs people a lot of money to attend a wedding - plus, have you never seen all the MN threads about how you should be wearing the same old dress, etc. ??
She needs to be speaking to the registrar, the venue, the caterers, the photographer, etc about what happens next. Reassuring them that they will be paid in full and when, where things need to be sent (food, drink, flowers), and if she needs to provide them with any further details to follow up on.
And then, when she has sorted out what needs doing, go away for her time out and to get her head together.
AFAWK the groom is the innocent party right now - no assumptions unless we are old differently. Why should he be the one left standing and sorting out the mess?
It isn't brave to just run away.