Well, we know she won't use a gun to do it.
What they really mean is "*I* can't be trusted with a gun, I can barely restrain my violent urges as it is! And if I, advanced & enlightened creature that I am, can't be trusted with firearms, then no one can!"
Case in point, the Million-Mom-March lady who shot someone to death a couple years back. What the hell was SHE doing with a gun?
Rosie was downright looney-sounding when she was going off on guns and saying all gun-owners should be in jail. Yet she has armed security guards. IF she wanted to do harm to herself, she'd probably try to get one of their guns to do it, regardless of how she claims to abhor them.
Sometimes people are irresistibly drawn to the things they hate or fear most.