Hello and welcome, tif21!
I'm a non-jw, but well aware of the pressure put on a marriage of a believer and UBM, despite all the assurances! However, I think the way it works is to first try to convert the UBM, and if that is not an option and the UBM is outspoken, pressure the believer to save themselves and any children from "spiritual endangerment", ( ) by separation if necessary.
Hope to hear more from you, Retro