I don't know the brand. (She's traveling right now.) but I know it uses something called "N" notebooks.

Checking Amazon just now shows that Moleskin has one of its own. But I don't know if that's hers.

Might well be Lamy?

https://us-shop.lamy.com/en_us/ncode-technology

I didn’t even know they were still around until recently. I always had Lamy fountain pens as a school kid, many, many years ago.