I don't disagree, Chechen bombings in Russia have used women for that exact reason.

It's a tired cliche, and I know it's not something you can do in the US, but Israeli's have a pretty good profiling system in place. You don't base it purely on race or gender, but they are factors with the biggest discriminator being your story under questioning.

It takes a lot of skill to pass as an old person (e.g. walking the right way); our intuitions are good at spotting there's something "off". And anyone caught disguising themselves as a grandmother would immediately be under massive suspicion.