That VS flight from JFK is almost the last flight to London - the latest is the 11.45 AA flight and as stated the passenegr didn't have time to make that (it leaves from another terminal).
I am inclined to agree that your sister should have aimed to sort it out at the time but we've all been in situations whwre we can't be bothered due to sheer frustration of it all. I know someone who VS left in the US for an extra day due to a mecahnical a year ago and they were given vouchers for 200 GBP to use against a future ticket, plus a hotel and meals. If your sister got transportation on that ticket then there is no way the airline will refund it, but they may still compensate her; your post implies that she did not travel but is not explicit.
I am sure a letter to Virgin Atlantic is in order; they use 'excellent customer service' as a key selling point for their sevices across the whole brand and you can use that as leverage. It can't hurt to ask and the sooner the better - I would try their corporate head office in the UK as a starting point.
[This message has been edited by james (edited 12-14-1999).]