Oh so you didn't get a stamp since you are a Visa exempt national. That's why I was kinda confused. You're right in that we will all find out the validity of the Study Permit when it is given to us in the airport and I too think it will most probably be the same as what the visa in the passport is.
She can get a stamp in her passport if she wants! She won't get one until she enters Canada though.
I believe you are mistaking a stamp in a passport for a temporary residence visa.
A stamp is given at the border by the CBSA officer. It has its personal identification on it, the name of border point and date.
A visa (also known in IRCC talk as counterfoil) is a pre-clearance in the form of paper (other countries might use wet ink formulas still) which visa nationals need to enter Canada. A TRV is not a stamp.
Visa exempt / non visa nationals for Canada do not need TRVs and they instead receive ETAs, the only proof of which is the number they are given for the ETA as it is not in physical form.
Both visa and visa exempt nationals can get stamps in their passports, but it is no longer normal but you can ask for a stamp in your passport, if you ask for one, some students need their passports stamped for residence purposes for their home countries to prove they are not there for example.