In Katherine Mansfield's "Her First Ball," the beginning of the short story tells us about Leila's state of mind, and the importance of this moment in her life. We find that Lelia is inexperienced. (The reader later learns that she has live in the country, and learned to dance while away at school.) The Sheridan girls will comment on this while they are traveling to the ball in the coach.
Leila's excitement (state of mind) is easily recognized first with:
Exactly when the ball began Leila would have found it hard to say. Perhaps her first real partner was the cab.
Those who have been to balls before would not be so "frivolous" (as someone might think of Leila's thoughts) as to imagine a cab as a partner. We hear from those with more experience—the Sheridans—at the beginning, who are amazed that Leila has never been to a ball:
"Have you really never been to a ball before, Leila? But, my child, how too weird–" cried the Sheridan girls.
The idea that one might have a first ball is not weird, but the Sheridan girls say so—so we can infer that they find it unusual, or perhaps they say this to imply how much more experienced they are.
Leila sees sharing a cab with them as less than desirable, as can be inferred from the following:
It did not matter that she shared the cab with the Sheridan girls and their brother.
Leila's imagination—her total preoccupation with the significance of this event—is conveyed as she likens the bolster in the carriage to a dancing partner's sleeve:
She sat back in her own little corner of it, and the bolster on which her hand rested felt like the sleeve of an unknown young man's dress suit...
Again, the whimsy of her thoughts is evident as she imagines dancing with this imaginary partner as...
...away they bowled, past waltzing lamp-posts and houses and fences and trees.
In that the Sheridan sisters' comment about her "weird" condition of having never been to a ball does not worry Leila attests to her state of mind—nothing can dampen her spirits. The fact that Leila sees everything around her as part of a dance (the "waltzing lamp-posts") indicates that this is probably the most important event of her life so far.
For Leila, in anticipation of this event, everything about the experience is wonderful.