Think before you speak...
two greens
I really think you should find out facts before you try badmouthing a reputable company. Your sister obviously had a bad experience, as did thousands of other travellers that day. Was your sister aware that the main terminal in GLA was closed until 15:30 on the day in question? All flights that normally operate out of the main terminal(including Loganair) had to use the second terminal at GLA. A logistical nightmare in itself. It was extremely difficult for staff to get into the airport on that day, as all car parks were closed and all roads leading to the airport were gridlocked. Hence the reason Servisair were operating with about 20% of their usual staffing levels. With several airlines cancelling flights - all BA,Easyjet and Globespan flights up until the afternoon - there were several thousand passengers trying to get imformation that wasn't forthcoming. At this point if I were your sister I think I would have headed as far away from the airport as possible and rebooked my flight. It was logistically impossible to get staff all the way up the passenger queue outside the airport to inform them of which flights were operating and when. Even the Airport Operator's (BAA) hands were tied at times with the police controllling the whole situation.
I fail to see how Loganair could make a profit out of this, as like you said the flight operated to LDY without your sister and presumably without lots of other passengers. According to the BA website your sister will get a refund or could have rebooked her flight. That means the flight operated on the day without the revenue it could have received but still had to pay all the operating costs. You also say that the flight went on to DUB. So are you saying that all the passengers should have been delayed from LDY-DUB whilst the plane waited in GLA for all the passengers to check-in? I think you'll find if your sister was travelling from LDY-DUB and the plane was stuck in GLA waiting as you say it should have then you would have complained at that as well!!!
Bottom line - you should change your original post as quite obviously, this airline nor any airline will be profitting from terrorist activity.
As for the customer service, take that up with the airline direct, but don't badmouth them, especially as you weren't there on the day. Stories tend to be exagerated, especially from siblings.
You didn't fail a Saab check ride by any chance did you????