Tell your friend congrats on opening a store. It's big step :-)
I see three big things right away....
Take pictures on less busy background (White, she can just use white or light grey posterboard)
Tags - She's not using all of her tags. It will be hard for people to find her. For example, with the hello Kitty hat, I would use
Girls hello kitty
ear flap animal hat
hello kitty hat
Description - is it kid size, adult size? How many other colors does she offer? What size it? what color is it? What material? How long does it take? It is made to order?
12 months- 3 years
3 years to preteen
Here is her competition on the Hello Kitty Hat. I think there are some great ideas here