The pepper blaster only gives you two shots. And would need to be aimed which is hard at a charging dog.
Stun Guns don't really work except to scare them away. And they'd already be biting her.
I'd say a fog pepper spray would be best out of those.
But a firearm would be better. How bad is her eye sight. If it's truly terrible none of the above will likely work either.
Does she have any other limitations besides eye sight?