On behalf of the TSA agent, she was doing what she was trained to do; I just work here. So higher-ups need to address any problems that the public has with this policy imo.
On the other hand...
If I, or anybody else, held something small like that toy gun to my neck, then I'd probably need a mirror to actually know what it was. So there are a number of things, pens, cigarette lighters, finger, etc., that you could hold up to someone's neck to threaten them with.
Also, will somebody please reference where in the TSA airport advisory guide that it warns about carry-on things that someone might think is a gun if you hold it up to their neck?