Welcome to the HealingWell depression forum. You have come to a good place. I am wondering if maybe you two spend too much time together. Being that you both work out of the home. People can get moody when in that situation. Though I am not saying that is all it is, but closed quarters can lead to getting edgy with eachother. So I think that plays a part of it. Generally when couples work, they don't see eachother as much and as they say, familiarity breeds contempt. And absence makes the heart grow fonder. So maybe it would be good to spend some time apart, not spit up, but each of you start doing things on your own with other people. Such as going to the gym, or out with a friend. Though you may already do that.
Counseling for you would help you to understand and deal with her depression. And help you if you are starting to get it. Also it is another form of support, which I think you could use right about now.
The best thing you can do is let her know that you are there. She is going to have down days where nothing makes her feel enthusiastic. Days where she is angry, and days where she cries. Is she getting help for her depression? If not, I suggest a doctors appointment, she might need medication or counseling. It would help both of you if you both went to counseling.
It isn't easy living with somebody with depression, and it is even worse being depressed. So you have come to a good place to get other peoples opinions on this. I hope that she starts feeling better soon. And I hope that you do too.