It must be very hard for you, I'm sorry for your challenge.
I think you're right, when your partner needs more time, it's better not to push her buttons for now.
I think what you can do is to obtain more knowledge about suicidal depression, including doing some google research, as well as giving BB hotline a call. And be prepared, if suddenly suicide is happening or very likely to happen you know how to react quickly and which emergency numbers to contact (as Sophie mentioned).
Meanwhile, be a good and patient listener, have more quality time with your partner, help improve her physical wellbeing (e.g. make healthy and tasty meals, help regulate her life), encourage her to reconnect with her social network should be helpful to her mental wellbeing.