She calls him Donald.
Seriously, it is adorable.
I heard her tell him, while sitting on his lap,
"You are a very good friend, Donald."
I am sure as time goes by and they grow closer (?) she will learn that his name is Ronald.
And she will just look at him and say, "It is? Of course it is."
And because he is such a very good friend, he won't make her feel bad at all.