She had the gun in her hand from the beginning.

And I think if she'd wanted to kill herself she'd have at least aimed for the head.
At that point nothing indicated she was suicidal. Why would she have done so? To punish/hurt Lelouch? Then I'd have done it in front of his eyes "Look at me, I'm dying because of you and you couldn't prevent it; I'll watch you from hell while you go crazy on remorse" instead of that remote place where Lelouch could have easily overseen her.

Point: Rolo had the better motives.