i see what you're saying and understand her worry's. and i feel ya, my mom can be uptight like that too. but what everyones trying to say is that a fullface is not neccissary for this type of riding.
it isnt, but my brother works at a bike shop, so he gets a huge discount on helmets. I wear it when i do mtb, and my old helmet that i used for street broke, so i use my full face