In second AK book there is the idea of "Hexagram Types".
Its a way to use a framework of how the system answers a question, to know what to look.
In this case, you can look at it with "Gain and Loss"(will they lose the marriage), or with relationships(Him, Her and Relationship) to see how they relate - problems with the Relationship suggest they may lose it, while if there is problem with him or her, can see why somewhat. Can also use Auspiciousness Divination Method and just look what challenges the marriage may face going forward.
Since the setting in this case is trickier then it looks, I would recommend using 1 or 3 if you decide to use that. If not, may be difficult to be sure where one is suppose to look to see how the question is answered.