What special things do they have that is reserved strictly for them?
When he comes home, how does he greet the people in the house?
Does he do things where he is specifically giving up an opportunity to do things with you in order to do something with her that she wasn't expecting?
Are her needs being met? Are they being exceeded?
Also, it might help is she has things outside the house and relationship that occupy her time and give her a sense of accomplishment. You're pretty light on details about living arrangements and how she spends her time, but if he is her conduit for interaction with the wider world, there's a big adjustment that would help.