Not sure if this is your intent but your comment might be coming off the same as, “Why don’t you just stop being sad?” To people suffering from depression. Mental disorders and addictions are legitimate diseases and can be extremely complex to diagnose and treat. It’s really unfortunate that Steve Harwell died under those circumstances. His music brought joy to a lot of people.
This may be overly cautious, but I recommend making a log and gathering evidence for if/when this escalates further. Keep in mind that at 17 she is still a minor, so there is an additional burden of responsibility that is imposed upon you and your partner in every interaction you have with her. Get dates, times, and statements from your brother and partner on the 2 occasions she entered your home and slept over, in particular. The last thing you want to deal with is a false accusation from this kid who does not seem to regard nor respect your boundaries, which you have set clear at this point. Get security cameras. Document everything ongoing. I personally wouldn’t block her texts for now.
Next step is to inform her legal guardians, in this case her parents, that she is not welcome on your property nor to contact you or your partner. I would do it in some form of writing - email or text, again for the sake of evidence. At this point the responsibility for her actions shifts to them. If she is on your doorstep contact them directly and expect immediate action. You can also inform them that you have concerns over her mental health.
Once these are done, you have real actionable choices that you can take. I know it sucks having to feel like a bad guy in this scenario, but it sounds like she needs professional help. Her parents are the ones to blame here.
Sounds a little like a torture chamber to me with my tinnitus.
I share that sentiment- that poor person. To society’s credit, I have not yet seen any posts or articles with an image or their identity. Hopefully it stays that way.