It's been a known belief that if a black cat crosses your path, you'd get bad luck. After Haru saved Prince Lune (who seems to be a black cat), she gets showered with presents that none of them she wanted; then she gets taken away by a bunch of cats; then almost turned into a cat while in the Cat Kingdom and...it just goes on. Those who are superstitious or know of it will get this.
On the other hand, in many countries (Japan included) black cats are considered to be good luck, which might make her encounter with Lune seem quite ironic given how it goes. But by the end Haru seems to be more confident and has evidently stopped pining over the boy she'd admired at the start of the film.
Haru's reluctance to become a Cat Girl vanishes, and she just is worried about going home after that. Well, if she'd not turned back into a human, there's this really handsome guy, who is titled, and so noble... What would be so bad about being a cat if Baron was your boyfriend?
Dating Prospects aside. Anyone who's gone through that awkward/boring high school years phase [or just dull/awkward life in general] can most likely relate to Haru's attitude. How many times one would wish that something of the fantastic happened to break up the usual routine, to offer some other options to life than the expected. Ones that allowed for more freedom to fit in...Attractive, no?
The story of The Cat Returns, while fun, seems somewhat more simplistic and derivative than most acclaimed Studio Ghibli movies, which makes sense when you remember it's supposed to be the very first work of a teenaged author.
How did Haru's mother not notice that her daughter was missing all night long? Is she really that distracted? Or did the cats do something? Say, make her magically and temporarily forget her daughter's existence, only for the spell to wear off once Haru came back to the human world? Did they do the same thing to Hiromi? One can only wonder...
Given that Haru had had time to go get a haircut and plan an early trip to the theater with her friend, it's possible the epilogue takes place a few days later. Haru's mother is shocked to see her up early, and at least the haircut would probably have had her home late in the morning, given that hair salons don't typically open at dawn when she was returned to her own world.
