It’s lovely that you care so much. In my very unofficial opinion, I would just say that you can choose how to be her friend in ways that are healthy for you, as you said. You are not her therapist. It is not your job to make her feel better or always be there to help her out of a funk. I think it’s totally appropriate for friends to step back when they need to, to say things like, “I don’t have the emotional capacity to help you with this at the moment. But I love you and I’m happy to help you reach out to a mental health professional if this is an emergency.”
I think it’s okay for you to continue to share your successes and trust her to deal with her own issues around that.
Basically, I think it’s one thing to tell friends that they are “low vibe” and to call out their mental health issues as if they are problems the other person is deliberately creating. But that doesn’t mean a friend has to step into a place in which they are always holding back or trying to behave in ways that manage their friend’s emotional reactions.
It’s not an easy line to walk, and it’s not one that I think people can get “right” (whatever that means) every time. But I think it’s a practice.
I know I have to manage my own mental health issues and I appreciate my friends who support me through them, but I try not to solely rely on them or expect them to make big alterations in their behavior in order to protect me.