She could wear a black adult sizes mantilla. I sewed mine to a headband. All you have to do, is put the headband on, and it’s fixed firmly and never moves.
I don’t remember a time when we didn’t say the family Rosary. Regarding the mysteries, it is good to have a decent sized picture book where you can turn the pages fro mystery to mystery.
My eldest brother,Maurice, had a cerebral haemoraghe at birth and was physically and mentally handicapped, but before he could even speak he already knew all the mysteries. I think it was around age 3 or 4. My parents used to put him to the test by announcing the wrong mystery. He would be upset and protest.
But then he was an exceptional child.