In The Goblin's Tail, does Michelle's appearance make sense to the plot?

The fairy's tail is an anime work that I have been chasing for many years. The tail of the goblin has made me hope for life countless times, but the tail of the goblin I have been chasing for more than ten years is finally coming to an end. I redrawn the leprechaun's tail 1 and more than twice. At that time, I was puzzled by the seven years since they disappeared. Later, I thought, maybe this is the pit dug by the author to push them to a new height again. What influence did Michelle's appearance bring to the plot seven years later?

First of all, we know that Michelle is Lucy's "sister", but Lucy has no impression of such a sister. At that time, Michelle brought the fragments of infinite clock to Lucy, which put the fairy's tail in crisis. In fact, all this is because Michelle is too simple to be cheated easily. Seven years later, Lucy and her gang returned to the guild after being unsealed from Sirius Island and found that everything had changed. Only their people at that time remained the same, and her father died a month before she opened it. Listen, do you feel too sorry? It's only a month away, and their father and daughter will be separated forever.

Perhaps because of this, the author wrote Infinite Clock to let us know that although Lucy's father died, Lucy still has a "sister" who has a very good relationship with her. Finally, because of the infinite clock, the "sister" who was forgotten by her returned to her side. Perhaps because her father can't accompany her, she will arrange such a sister for Lucy.

Michelle was actually a doll made by Lucy when she was a child, because Lucy was an only child and always felt lonely when she was a child. Later, I made such a doll and named her Michelle. When Lucy was a child, Michelle grew up with her, so after an infinite clock, Lucy had another family member.