Did he or she tell the salesman they liked to play games? Such as statement could swing a recommendation (especially if interpreted as "Call of Duty" rather than "Minesweeper").
You know better than the Apple guy, but if your sis does not trust your opinion and did not tell the Apple guy what she needed then what do you expect?
I recommend to my sis-in-law that she get a Air for her 13 year old son because I knew that the SSD makes a BIG difference.
The Apple shop sold her a MBP because quote "it's faster".
Yes, the cpu has a higher MHz but please.