What do you do when someone you love continues to threaten suicide and won't get the help they need?

My mom. She’s 76 and has been doing this for decades. Two of her four children aren’t speaking to her now because of her occasional angry outbursts; the other two of us are hanging on and reassuring her we love her, but apparently that isn’t enough because she still wants to kill herself. Mom posted on Facebook tonight: “goodbye”.

Do we ignore these empty threats she’s been doing for decades now? She’s weaseled out of appointments to get help in the past. She just won’t see anyone. What else can we do?