This is complicated, as the responses above suggest. I have a few thoughts, some drawn from personal experience and others drawn from my work as an inpatient psychiatrist at a public hospital. These thoughts may contradict, which demonstrates how difficult it is to tease these things apart.
1) suicide threats are always serious and dangerous.
2)Besides her age, here are some risk factors that would increase my level of anxiety if your mom were my patient: alcohol or other substance use, degree of participation in her psychotherapy and pharmacotherapy, previous attempt, family history of completed suicide/suicide attempts, diagnosis of bipolar or depression, poor social support, other life stressors (poor housing, precarious income, etc), hopelessness, despondency, impulsiveness. Of course, there are others and these are not absolute.
3) some factors that would reduce my anxiety: her female gender, tight family, religion, future plans, good-to-adequate self-grooming such as recent hair cuts/manicures/new clothes, etc, friendship network, fulfilling occupation. Of course, there are others and these are not absolute.
4) what does she gain when she threatens suicide? Does the act of threatening reduce some sort of existential anxiety or guilt? Does it gain her some positive or affirmative contact? Are there more adaptive ways to provide whatever she gains? Ways that are not so distressing to you.
5) What does she live for? The problem with suicide is not that it involves death, but that it means that the person did not fully live life. It also means that the people around them had to suspend fully living their life to care and process the suicide. Is she living fully? If not, why not?
6) How are you doing? How long have you taken responsibility for your mom’s mental state? Children (no matter what age) are not responsible for their parents’ happiness. We may take responsibility for organizing their meds, getting them to appointments, etc, but not their satisfaction or dissatisfaction with life. It is a deep and powerful betrayal when the child has to assume the parental role. Know that when I read your question I was deeply concerned for you, your development, and your present ability to live your life the way you want to live it.
7) Sometimes, despite are very, very best efforts, we can’t stop suicide. It crushes me when one of my patients completes suicide, but some people are difficult to reach.
8) Best thing you can do for her is make sure you are healthy and well enough to care for her if you need to. Dont burn out. Remember that you love her. Chose your actions from the principle that you love her and that she loves you and that you both want whats best for the other, even if nasty words are said, transiently.
9) Trust your gut, not your brain. If you are truly scared, call for help. If you feel she is bluffing, respond based on your tolerance for risk. Operate from your best intentions, let the pieces and consequences fall as they may later. Remember, in suicide, only one person chooses. Only one person bears responsibility. It is not the family’s fault, no matter how often you second guess every little thing you said or did.
10) If you mom does get admitted to a psych unit, go visit her daily, bring her clothes, food, stuff she likes. It’s OK to have public display of affection on psych units. It’s OK for families to cry (just don’t yell). Make sure she doesnt have a chance to forget/doubt you love her.
11) Should your family be the victim of suicide, god forbid, don’t stop living your life. Give tribute to your loved one and live as fully and as authentically as you possibly can.
Hope this helps.