Visa needs for Vietnamese wife American husband

I will be traveling to Ho Chi Minh City with a friend to see my wife in January and we would like to stop for a couple nights to visit a friend who lives in Zhuhai. I think my friend and I will qualify for the 72 hour transit so I need to know what the requirements my wife has. If she stays less than 24 hours or if she stays up to 72 hours with us.

Thank you
Jason