Not from inside the United States. TD status permits presence and study but not employment, and serving Canadian clients from a U.S. address is still work performed in the United States. She would need her own qualifying status or work authorization.
Remote work for Canadian clients is the most common misunderstanding
The employer being in Canada, the clients being in Canada and the money landing in a Canadian account do not change where the work is performed. If the spouse sits at a desk in the United States and does the bookkeeping there, she is working in the United States. On TD that is not authorized. The practical options are for her to keep the practice but perform the work only while physically in Canada, to pause or sell it, or to look at whether her own qualifications support a separate status — Accountant is a listed TN profession with its own credential rule, for instance. A child on TD may attend school and may not work, including summer jobs. Write each person's intended activity down before the move so that nobody discovers the limit afterward. Household plans that were never examined are the ones that create trouble at a later entry.
Hypothetical example: the spouse of an East Hants maritime rope-access inspector plans to reconcile invoices for her Canadian climbing-equipment business after the move. The first review should list where she will sit, which tasks she will perform, and whether any work will occur during U.S. visits. Client addresses and the currency of payment do not answer that question. A dated work calendar and a plan to pause U.S.-based activity are more useful than a verbal assurance that the business remains Canadian.