Well, your sister ain't wrong about that, even those who did know and did see the signs usually like to pretend they didn't, or they were too frustrated by the suicidal person that they didn't want to bother with them..and then feel guilty when the time comes.
A worse thing to say is "I wish they came to me, I wish they knew how much they were loved. I know that if they knew, they would not have done this."
God damn this type of commentary repulses me. Just putting the blame on the dead person and believing that "their love" (and knowledge of that love) would have saved the person or been enough for them to continue on in misery. It's a very self-centered way of thinking (and they call us the selfish ones..).
Once in a blue moon, an individual left behind may have good reason in saying or thinking something along these lines-pondering in hindsight, but that's usually when the deceased person "had it all" and always pushed people away from the beginning, even safe & understanding people (maybe even being a dick about it), all the way up until the end, or for those who blindside everybody by killing themselves on impulse, never even allowing an opportunity to intervene or empathize.
(Occasionally I do feel sorry for those who truly had no idea, and only wanted so much as a chance to say goodbye, nothing more.)
Ultimately, people are busy with their own lives and will not stop to help you with yours, until it affects them, which death and a funeral usually does, ironically more so than suffering loudly in close proximity.
They will pause for your death, but not for you.
And then they will step forward once again.
If anyone in my family (or otherwise) tried to pull that shit, the whole "if I had known" shtick, they would be some incredibly disingenuous folk.
They only say this when you're already dead, when it's already too late. When you won't be there to hold them to it.
None of my own family members even ask about me or bother to respect or acknowledge my pain and suffering-and everything that was starved of me or lost (except my mother, but only on occasion, and only to a certain minuscule degree) but man oh man do I ever ask and hear about their shit..constantly.
Even though not a single one would last a day in my shoes.
I don't go around announcing my issues to most of them because I already know they don't give a rat's ass, as most of my shit should be obvious, including the fact that I am isolated and gave up on the charade of a rat race that they still compete in, because I didn't make the cut at the starting line.
They don't care, it's as if I don't exist, they chalk me up as defective and a lost cause and go about their lives.
(Being dead won't make much of a difference.) I'm an embarrassment to them.
...
In their eyes, they're somehow more of a victim of life than I am, simply because they only view the world from their own perspective and are so insanely myopic and egotistical that they cannot see (or purposely turn away from) the much more severe torture endured by a person so close to them (going as far as to contribute to said torture..right in front of my face).
If I ever have to interact with anybody, I feel like the fakest motherfucker that ever walked the earth, taping a forced smile over my grimace, presenting myself as a spaced out doormat, dying inside every second I am expected to act like I'm not.
If they saw the real me, the damage..after all this time..they would probably blow a gasket and run for the hills, using my pain and hatred as a way to further demonize me and victimize themselves.
I've dipped my toes into that dark water before..never again.
I really try to keep to myself-all that ails me, for this reason and many others.
Meanwhile those who have much superior quality lives/privileges/opportunities are complaining all. the. damn. time.
They just never shut up, and social media has made it so much easier for them to whine about absolute bullshit.
Some of the most '#blessed' people act like the biggest martyrs, they have more energy than the rest of us to keep it going, and a larger audience to enable them.
It's so ironic, a lot of the people suffering the most are the ones we never hear from, or about. It's a sad affair. A sick joke.
If I had a terminal illness all my life and a relative of mine suddenly became ill, if I so much as spoke of my own experience to relate to them..they would act like I was "copying" them. (I know because a similar scenario has already occurred, multiple times.)
When I've been here all along, existing in a constantly compounded pile of shit.
That's how out of touch they are, a willful and narcissistic lack of awareness.
And because I have learned from experience that trying to have a conversation about my own woes is met with awkward silences (or worse)..my conditioned and expected lack of openness only perpetuates their ignorance and lack of sympathy.
It's a cycle that I did not start, but must suffer under. It's maddening.
I'm so sorry you have had to experience a similar dilemma, especially when your mother has an event equivalent to premonition, and should realize that the same thing that possibly happened to one of her children, could easily happen to the other.
I think though, that when parents lose one child, especially if that child was favored (was he?) they lose even more sight of the rest, almost as if it doesn't matter if it happens again, because their brains are already broken and conditioned to the impending loss. Losing one can be like you already lost them all, at least that is what I have noticed when researching the aftermath of several suicides.
Still unfair to you, however.