We both usually experience pretty moderate seasonal depression and we both have our ups and downs on regular sunny days as well. She came home from a day out with her friend who was Christmas shopping for her husband and family and I could tell something was off. 

I may have pushed too many buttons because I didn't know what was happening so I was definitely nitpicking and annoying her. 

Realizing that she was hitting a low, I went and washed dishes so I could leave her alone and get things done also. She went and showered. 

I had just sat down when she texted me from the bedroom asking if I could give her space. She said that it got really bad today (the depression) and she doesn't know how long this one is going to be. 

I feel like I've done all that I can but still completely useless. I offered to sleep on the couch and she told me to just come to bed after she falls asleep. 

Am I crazy to think that I've done something wrong? She swears I haven't and I believe her. I know everyone is different but when I hit a big low like this I want to be with her and be held and be talked to. 

Is there anything you think I can do?

TL;DR--Wife has severe holiday blues and I feel like a shitty husband after she asked to be alone indefinitely

Apologies for formatting, I'm on mobile.