Honestly I've been struggling with incredibly severe (DIAGNOSED) OCD for the past 2 years + sexual abuse trauma and wouldn't treat my friend like that. When I meet up with my friends, there's a couple of things I do:
- Try to make sure to ask for permission before discussing depressing/dark stuff, and if they say 'no' then I respect that and keep to light topics
- I always make sure to ask about how my friends are doing and keep abreast of the stuff that is affecting them (as I'm not the only important one in the friendship!)
Honestly it might seem a bit weird that I have 'rules' on this stuff, but one thing I know is that mental illness can make you incredibly small-minded and selfish, because it makes you focus on yourself and wallow in your own pain. I never want to take my friends for granted/treat them like shit, so I make sure not to let my mental illness destroy our relationship. This obviously doesn't mean that they don't support me (my best friend especially has been amazing and will pick up my phonecall at all hours) - it just means that I support them as well.
Your friend refusing to get treatment is a major red flag. It is, of course, a symptom of mental illness ('nothing will work, what's the point'), but it's also a problem b/c it means that she isn't taking accountability for her own recovery. If she's not actively working on recovering it means that she probably won't get better, to be honest. It's hard but the only person who can recover from mental illness is the person who suffers from it. There's also the element of she's essentially using you as an emotional dump, which isn't fair. You aren't free therapy, you're a human being. She should want to spend time with you because she genuinely likes and cares about you, not just so she can monopolize the conversation and vent to you. That's not ok, and her mental illness actually doesn't excuse her behaviour. You've literally been through bereavement recently which is a terrible thing to happen, and yet she didn't ask about you once? That's genuinely horrible.
I'll be honest, she sounds very self-absorbed so personally I wouldn't bother having the conversation of 'please treat me better' with her, I would just start to distance myself. It sounds harsh, and usually I am all for telling my friends when they've upset me instead of just drifting away from them, but she doesn't really sound like a friend, so continuing a friendship with her is pointless.