From my own personal depression, it got really bad when I ended up trapped in a marriage that really never had live at it's foundation even when "I love you's" were expressed.

Give her her space & see how she does. I thrived & my deoression went away as soon as I left my marriage after 33 years.

If it doesn't improve for her then you know it wasn't the relationship adding to her depression.

I serioualy think there is much more to her lack of live than just her depression.