In L-2 she is authorized to work incident to status, so immigration permission is not the obstacle. Practising as a nurse requires a licence from the destination state and, for entry in certain health occupations, a health-care worker certification, both of which take time.
Immigration permission and nursing licensure run on different clocks
The L-2 spouse rule gives her employment authorization as a consequence of her status; employers can accept her annotated Form I-94 as proof. She could take non-nursing work immediately. To work as a nurse she must satisfy the state board, which may require an English test, a credential review of her Canadian program, an examination and a background check, and the sequence can take months.
Ask the board in writing before the move. Separately, federal rules require certain health-care workers to hold a certification from an approved credentialing organization; the requirement is tied to the occupation and the admission category, so confirm with counsel whether it applies to her plans as an L-2 spouse. Children may attend school but cannot work.
Her L-2 status lasts only as long as his L-1B, which is capped at five years, and a later change to another category would need its own analysis. A first review makes a family matrix listing status, intended activities, local permissions, and document expiry for each person. Hypothetical example: a high-voltage cable-testing specialist’s spouse plans to accept a job as a dental-office administrator.
The admission record resolves the immigration authorization for the spouse, but the employer may still request tax and identity documents. Confirm the child’s study plan separately, because a dependant child cannot take paid employment merely because the spouse can.