Husband & Wife Controlled Group Question In Setting Up Plan(s)

Good morning!  I'm just trying to see if we can setup an additional plan for someone due to it being a controlled group:

1) Employer #1 - Husband owns 100% of the company, his wife is the only employee

2) Employer #2 - Wife owns 100% of company (and is the sole employee)

So the question is, the wife is getting a benefit under her husband's Plan (and a sizable one).  Can she also setup a Plan under her own company or would that not be allowed?

What kind of businesses and what kind of plans? 

Yes, but she would have one aggregated 415 limit on like plans (one DC limit, one DB limit) so there would be no advantage to her business adopting its own plan. Depending on her pay in husband's business, there could be an advantage to having her business adopt his plan as a participating employer, or adding a new DC or DB to the CG if there is currently only one plan.