Hi there, I had applied to pharmacy and med school at the same time during my first cycle three years ago. I got Rs at all my med schools before interviews so I can't really answer all your questions, but I got into pharmacy so I can address a bit. I can say that I don't think it's that common a back-up, most of the students in my pharmacy class knew that's what they had wanted to do. Of course maybe not everyone is willing to share that it was their plan B... but our school also has a pretty low dropout rate so not many people going back to med (though this could be because they gave up now that they're in a professional program).
If your cousin has experience volunteering or working in a pharmacy and can see themselves enjoying that then it's great, but the pharmacy profession is in a weird place right now. In Ontario, they've been pushing to gain prescribing rights and were only able to get this recently but the legislation putting it into action is still in the works. On the other hand, automation and electronic stuff is constantly threatening the future of pharmacy. The market is also very saturated right now especially in GTA.
In my experience - I really enjoyed learning in school, but being in a community pharmacy environment and contending with stuff like insurance and irate patients and corporate shenanigans like cutting hours for the staff etc is what really pushed me away from it.
If your cousin has any specific questions feel free to PM me and I'll be happy to help however I can.