So my first response is obviously your friend has fallen off and hit her head to come up with such a ridiculous statement as helmets cause more injuries then they prevent.
Frankly it comes down to its your life.... do you want to take a risk of living it in a wheelchair with a family member or hired help changing your diapers and wiping the drool from your mouth?
Yes I know there is no guarantee's that this will or won't happen... but that's the lottery you play when you don't ride with a helmet.
I'm at home now recovering from a fall - and even with the helmet I ended up so concussed that as I got up to walk over to my horse I fell down again and had a full on seizure. I will tell you NOTHING in my life (and its been a long one) prepared me for that feeling. Your body is reacting and you are just along for the ride.
That helmet saved me from the likelihood of permanent brain damage. And that was just from a single buck coming off on sand. A helmet has actually saved my life two other times. Once on pavement - lost my memory for two weeks and ended up in the hospital. Never did get those two weeks back.
And another time again on soft landing but bounced over to a rock. Split my helmet.
I know wearing a helmet is a choice, but frankly why would you risk it. Is it pretty - no - but neither is brain damage. Will it protect your neck... nope but if that becomes a concern for you, then I would invest in a blow up vest. Which after the number of accidents of recently I've suffered that is my next step.
All it takes is one bad fall - and no one knows when that's going to happen. I can give you list of extremely talented and experienced pro riders whose lives were saved by helmets. I suspect that they are as talented as they come, but when your number for coming off is called, even the most talented cannot stop a fall from going sideways.
Good luck with your choice.