A set of journaling pens/markers
Some pattern paper -- as was said before, maybe a collection of pattern papers in a color palette your mom likes
Cardstock -- I'd probably stick to white, kraft/brown and black...or colors that coordinate with the pp given
A 6th would be adhesive, but I've found that I needed to do trial and error on my own to discover what I do and don't like. So maybe see what your mom has access to and let her pick what she thinks she'd like (by the size of the dispenser, etc.).