Co-sleeping can be highly beneficial for both mum and baby. Have you researched it at all? Western culture is one of the few where it isn't commonplace ...and it has the highest prevalence of PND. This may not be consequential but in my personal experience, I'd be surprised if they couldn't be linked.
At nine months it's unlikely your DD is suffering separation anxiety from you, don't worry. They tend to be quite flexible and accepting of changes to their living circumstances at this age.
How long ago did your DW ask you to move out? She sounds very down and it can feel nigh on impossible to support someone through depression without risk to your own emotional health. Have you seen a GP yourself about how low you are at the moment? You need to look after yourself to be of any use to your family whether together or apart.
You and your DD have a right to spend time with each other. If as a consequence of her PND, your DW feels more comfortable with you doing so with her there, then this may be for the best for now, unless there is a third party you could ask to become involved?
Your DW can't use this time to give you a hard time, it should be strictly for you and your DD to enjoy, with your DW in the vicinity only. Similarly, this is not the time for you to make attempts to discuss matters pertaining to your relationship with your DW.
If she is refusing to allow you to see her at all then I think you need to seek legal advice. Mediation may help in this situation.
If she wants to separate, you have to work on acceptance of this, no matter how difficult this feels.