Chowing in Banff?!
As Banff is a tourist town the food scene can be rather expensive. Having said that, there are a number of pubs (Rose and Crown; St. James Gate) in town where the food is not bad. Another place that is pretty good is Earls. Also, if your sister and BF can afford a splurge night they should give Fuze a try.
Speaking of Fuze, I just got their email newsletter. Starting on Wednesday they are having a local's special (through to Dec. 15) that is open to everyone. An Aromas of India 3 course menu for 45 bucks. While their menu is very international note that their chef is east indian. Could be very nice.
If they want cheaper bar like food, Tommy's rocks.