I'm very sorry that your wife is in so much pain.
Pain is a terrible thing and when she says she wants to die then she's probably meaning that she's had enough with pain and she wants the pain to go away.
I'm not sure what treatments or medications have been tried and as I don't have TN myself so am not sure what is available.
I just saw your post and needed to reply to you.
If her pain is still so bad she really needs to go back to the doctor.