Sorry to hear about your sister's misadventure, but it does help to keep a sense of perspective.
Yes, BA has a serious problem with baggage at the moment. However, unless your sister's vist to Toronto was very short, it is rather extreme to say that her holiday was 'ruined' by a delay in baggage delivery of two days.
As regards the delay on departure from Toronto, yes, BA should have provided food and drink commensurate with the delay, as per EU Regulation 261/2004 as Jenbel stated, but, again, let us keep a sense of perspective. Your sister would have had a seven hour wait at LHR. Instead, she got five of these in YYZ. Not ideal, but hardly the cause of a 'ruined' holiday.
Your sister would definitely be entitled to reimbursement of any purchase resulting from the delayed baggage or delayed departure.
So, if she had to buy any clothes, toiletries, etc..., she should ask for reimbursement of these from BA (they will normally ask for receipts). Similarly, if she bought a meal/drinks at YYZ on the return, she would also be entitled to reimbursement.
Anything above that would be goodwill on BA's part. She might get some FF points if she is a BAEC member, especially if she is a silver or gold member, but don't hold your breath. She is unlikely to get substantial compensation above and beyond reimbursement of expenses.
She can contact BA customer relations by email from the BA website. Alternatively, she could contact reservations in Mauritius (+230 202 8000) and ask them for contact details of customer relations.