Being Canadian citizen, she can take some advantages

As Canadians can drive through the US port of entry on Canada/US borders without B1/B2 stamping on their passports, CIS may not have their entry records at all.

When TN/TD holders drive back to Canada, they don't have to I-94, even if it is expired.

So she can simply take the US/Canada free travel advantage, and does not need to leave the US and to re-enter for changing status to B1/B2. CIS does not care her B1/B2 record in its database or not, as Border Control logs less than half of Canadian enries.

BUT she cannot stay for working in the States, without employment authorization.