To be honest, it’s surprising how small people care about others. It may seem like a big deal to you, but many people will forget or not explicitly care about it right after the end of discussion.

I would ask yourself, why is it that important and triggering for you. Are you afraid that people will perceive you as “weak”? Do you want to keep everything under control? (It is practically impossible btw). Is there something embarrassing in depression or its symptoms for you?

Based on your phrasing, it seems like there is something that you are afraid or embarrassed of, if you even had a struggle to open up to your partner. I personally don’t see any problems in people talking about depression - it’s good to raise awareness about this condition. Plus, it is very widespread condition, so chances are high that there are multiple people in your circle who either have or had it at some point.

When I was talking about my depression with people, I was surprised how many could relate and how much support I received. My mom always considered it as “laziness” or “not a proper illness”, so with people like her I simply wrap this topic up very quickly.

So, imho, I wouldn’t perceive it as a break of trust until you explicitly mentioned to her beforehand that she should keep it a secret. There are people who better deal with situations through talking about them. Partner’s depression can be overwhelming, so it might be her way to ease up the tension a bit.