Shouldn’t impact her vacation entitlement to the extent she gets at least the vacation time and pay required in that province for an employee with 10+ years of service.
Cutting back her workload would definitely involve legal risks. The first would be constructive dismissal if the reductions in hours and resulting wages are significant enough. Constructive dismissal depends on a bunch of factors but big hours and wages cuts are definite red flags. The other risk would be age discrimination. Again, that would depend on the context and whether there’s any evidence to suggest that the company is trying to force the employee out due to her age, e.g., derogatory remarks or inappropriately asking her about retirement plans.