Sorry, I keep writing posts when my phone is on low battery and posting them before I’ve finished!
It is extremely rare that a person who commits suicide gives any warning. Most pretend to be fine, happy, moving forward etc. It is these people that don’t want you to know and don’t want to be stopped. Please don’t torture yourself over this. The important thing is she is at peace now and wouldn’t want you to be sad. The pain at the end I suspect is a relief - the ending of the pain that they just can’t live with anymore.
Are you close to your parents? Are you the youngest, eldest? Can you talk to them about it? I sound like a broken record, but talking about your grief when you are ready is really important. And we are here too. My heart breaks for you. Such young and beautiful lives lost really are a tragedy.