Hopefully we don't have the whole story, if we do, I'm shocked by the actions of the F/A presented with the text and obvious hysterics of the passenger which surely couldn't have been a standard, "but I need to make a call" excuse. I do have my doubts for many of the reasons stated already, namely the involvement of other pax or the lack there of.
That being said...
Very, very interesting example of society. Like others have said, if that was me, not sure what my logic would be at that point as far as who to call first, but I'm getting the hell off that plane. But everyone is different, and I'm honestly not one to hesitate to do what I need to do regardless of how it looks to others. I'm sure that many, many people in this country would have such mixed emotions and anxiety in that situation that they would still follow the basic "airplane authority" and submit to the crew. So this does not surprise me at all. Terrible chain of events though, I'm sure even if the cockpit crew didn't have all the details, this had to be hard on them once they found out.
I'd like to think pretty much any crew at Southwest, with a full understanding of the situation of course, would have at the very least let her make some calls, if not return the gate or have the F/As counsel her to dial 911. People go to work to do jobs because they need money to provide for themselves and their families, but they're still people. Being a human means having the compassion to know when to stop being an employee and start being a person. Hopefully there aren't any monsters out there who would feel otherwise.
As far as the suicide, who knows. Maybe she didn't grasp just how far gone he was, it could have seemingly come out of nowhere for her perspective. But with the details at hand, I really have to think he hoped her phone would be on airplane mode already and she wouldn't have a say in stopping him. Likely planned it that way unless the timing was pure coincidence, which I doubt.
Wouldn't want to be that F/A right now.