Tweeny Witches is clearly meant for children, probably for eight to ten years old - and in that aspect its story is very well crafted and uses the hero's way trope, effectively adapted for a child protagonist.
Alice wants to be a magician and one day she ends up in a twisted magical land where warlocks and witches are fighting a never ending battle - until their whole world seems to fall apart. Only Alice and her friends can save the realm. The magical journey is a typical setup (from Magic Knight Rayearth and Escaflowne to Twelve Kingdoms and many others), but this time the message is clearly aimed at children.
The young heroine must deal with an unknown world (initiation) and has to save this magical world in order to be able to return to the human realm (so her childhood self must be protected and integrated in order to face adolescence); eventually she will have to save her family (offsprings outgrowing their parents) with the help of friendship and wit. The answers are genuinely universal and to my greatest amusement the whole setup is not very typical to Japanese animation.
The animation and the artwork is beautiful - neither typical japanimation, nor the the American school; when it's not trying to cut corners (with lackluster transitions or weird camera angles) then with its flat coloring and strong curves it resembles Art Nouveau posters and drawings. It is understandable why this TV series is not very popular, but it's coherent and well crafted, probably children can enjoy it much more than grown up reviewers.