No. A benefits plan does not determine dependent eligibility or permission. TD does not authorize employment.
Keep employment benefits separate
A relative’s actual category, relationship and admission records need their own assessment. The dependent category is for a qualifying spouse or unmarried child under 21; each person needs valid status.
Work performed physically in Canada is not US employment and does not require TN status, but it changes the record: the applicant becomes an existing employee whose US entry must be as a TN professional, not a visitor. Consider whether the spouse might work remotely for a Canadian employer in the interim, and confirm separately whether that arrangement is workable while in the US on TD status, since remote work still raises its own questions. Dependants hold TD status, which authorizes residence and study but no employment of any kind, and working remotely from inside the United States for a Canadian employer is still work performed there. TD permits study but does not authorise work of any kind, and remote or unpaid activities require individual review, so a spouse cannot lawfully replace the lost income on TD status alone. If the promotion changes the household’s location or income expectations, identify the spouse’s actual proposed activity and have an appropriate work basis assessed before committing.