First off- I am so sorry for your loss.
I have a very good friend who is a ped dentist. I just eamiled her recently about my kids teeth grinding. Here is her response:
Teeth grinding in children is extremely common! It's nothing to worry about, and it is NOT related to stress.
They grind their teeth for a number of reasons: it makes a cool noise; they like the vibration; it becomes a habit; it gets attention; they are unconsciously adjusting their bite, and it helps to open their teeny little Eustachian tubes. Can't do much about anything but the latter; if you think she might be congested, or have allergies, relieving the source of the allergen may stop the grinding.
Teeth grinding often persists until all their permanent teeth are in, which is around age 12. It can also get worse during the mixed dentition stage (when they have some baby teeth, some permanent teeth). They seldom do enough harm to the teeth to cause concern.
I wouldn't worry, but I might buy earplugs!
Very rarely does it do enough damage to warrant intervention; by the time they wear to a worrisome point, they fall out. I *have* had a few children on whom I've put a protective covering over the worn teeth. It doesn't stop the grinding, just makes them wear through *that* before they get to the tooth structure.
Mouthguards are pretty expensive, and in a child, their mouth will change practically monthly. So every time they lose a baby tooth, or a new one erupts further, you'd need to have it remade. So no, it's not usually recommended. I've actually never done one for this purpose in a child.
I wouldn't worry about it at all at this age.