I haven't read those but I've read Canaan's "A Pony For Jean" (beautifully illustrated by Anne Bullen) and which is surely the reason that the first Jill book is called the rather odd "Jill's Gymnkhana" and not the more obvious "A Pony for Jill", because this would draw attention to the fact that so many key elements are surely based on Cannaan's book. (I do love the Jill books as I've said - but the first one does owe a lot to Cannaan.)

"A Pony for Jean" is very amusing with a lovely narrative voice also - again, I'd highly recommend it.