Someone doesn't have to outwardly show depression for them to be depressed. I just kept things inside a lot, even though I was really depressed. When it started causing problems in my marriage I finally told my spouse after a few years of struggling. She said she didn't realise it at the time, but afterwards when I told her she could piece it together. To me it sounds like she is withdrawing, that is a good indicator.

Depression is kind of a broad term and it could mean a lot of things to different people. On the low end it is a state of boredom. A type of monotony. Where you just kind of exist. Your not happy, but your not miserable. Just bored and kind of existing.

After that there is a state of sadness and hopelessness. You are completely withdrawn from most things. You lost interest in most areas of your life. Possibly consider that life is meaningless and contemplate suicide.

Beyond that there is apathy. You just give up on even caring. You don't do much in the way of personal hygine, extreme fatigue, excessive sleep, or very little sleep. You are completely disinterested in everything. Even self preservation is diminished.

There are levels of depression, and she doesn't have to be ready to jump off of a bridge to be affected.

It sounds like you want things to work out and are stuck. That is because you sort of are. You can't make her care about the relationship. You can voice your concerns and try to talk and tell her you are unhappy. She can either address the issues or not. If she doesn't you have to decide if the relationship is worth it to you.

It sounds like she doesn't want to fix anything, or is unwilling. If I were in your position I would be honest with her and tell her all of the things that are bothering you. If she is unwilling to address any issues then tell her you will leave the relationship.

It could be depression, or it could be she just doesn't care that much and is content in how she is living her life. If that is the case you have to decide if that works for you or not and make your decision. Unfortunately we can't make anyone be the person we want them to be. We eventually have to accept who the person is and he happy with that. You can't make her care or be passionate about your relationship, that has to be her decision. Good luck to you. It sounds like you are in a delicate situation.