Replying to My Girlfriend is going to kill herself, HELP

My Girlfriend is actively talking about suicide, and she keeps telling me to leave her alone because she doesn't want to hurt me, that she has nothing to live for. She says the stress is too much, and that she's dug her life into a hole and she needs to die. I don't know what to do, i'm shaking right now, crying, I feel like a terrible boyfriend. Please help, what can I say?

She lives 300 miles away so I can't go visit her or anything. She won't Sykpe me. I feel so helpless

Please NS this is not a troll, I need some help