it's important to note one thing. somebody saying they'll harm themselves if you dont do ___ is JUST as manipulative and abusive as them saying they'll hurt YOU if you don't do something. both involve violence; one just uses fear while the other uses guilt and empathy. if somebody is trying to manipulate you by saying they'll hurt themselves, you don't owe them anything and it's better to get away from that toxicity for the sake of your own health.
if they actually do something to themselves, it would NOT be your fault. you're not responsible for their life and can't help them when they need professional mental help.