It might be slugs or some sort of caterpillar. It doesn't look like too much has been eaten. I wouldn't use an insecticide but I would carefully check the entire plant for caterpillars, especially baby hornworms. If it turns out to be slugs a ring of diatomaceous earth around the plant will keep them away. If she finds caterpillars I'd pick them off by hand. They camouflage themselves very well and can be hard to find.
Karyn

Karyn1 is right but I don't think it's slugs as I don't see the slime trails they are noted of leaving. I would look for worms or cats on these. A nice small pair of nippers or sissors work great to cut them in half. You could also strip off the lower leaves that were damaged.