Lily's dialogue is written in an idiosyncratic style. Almost every one of her sentences ends with an additional tiny katakana that either repeats the final vowel or cuts it off with the glottal stop ッ. In effect, this means she talks with a shrill voice, with a rising, stressed tone at the end of most of her sentences.

Basically, she sounds like a tsundere.

(The kind with a sharp tongue. Nearly literally so, tone-wise.)

I try to reflect this in the translation by giving her a brusque manner of speech and adding exclamation marks when appropriate.