It’s perfectly fine to change Starlight’s pronouns. (I agree with your assessment of their personality; Liza’s also kind of she/they-ish, but I’ll keep her she/her since I think both would work.)
————
~Liza~
“How is it?” Starlight asked Liza, presumably talking about the food that both of them had ordered. Liza was too busy eating to answer–the cheese-and-spinach pastry was delicious, flaky on the outside with a filling that had just the right amount of cheese in it to make the whole thing creamy–a far cry from the boiled greens. She took a sip of her summerlily tea, which was also wonderful. It tasted like sunshine and flowers and gardens and frolicking and happiness.
“It’s really good,” said Liza, which she felt was an understatement. “Everything tastes amazing and the pastry and the tea go together perfectly.”
“Mine too,” said Starlight, drinking their lemon-fizz. “The soup is warm and comforting, and it smells so good…”
The tea reminded Liza of her childhood in Mer with her aunt, who had worked at the city’s botanical garden. Whenever Liza wasn’t in school, her aunt would take her out to the garden. Sometimes, Liza helped tend the plants, but more often she simply walked around, taking in the beautiful sights and smells of the flowers and trees, or she read, either while lying on the grass or while sitting on one of the many benches. Liza got to know the garden very well.
“This tea reminds me of spending time at the botanical garden where my aunt worked,” said Liza. “Funny, how tastes can be so strongly attached to memories. Does any of your food bring back memories for you?”

top – since it didn’t say I replied