How to best tell good tenant you want your property back

[Johnson Best]

A tenant who is paying on time without much problem except over a year ago her husband caused a big scene and now by law barred from my property.  

I need the property back for other purposes.  She knows the rental rules pretty well, and she is paying below market rental price.

How should I best inform her both humanly and legally and not missing any steps so she would have minimal confrontation from her?  

Thank you so much in advance.