Ah yes, my bad, you are correct. I meant to say that it's not simply that the distinction is between "named individual" and "stranger" but is more complex.
It seems like "they" is used 'correctly' for a singular subject when the subject has been previously referred to, but hasn't been given a proper name. But I'm sure a linguist has studied this in further detail.
Some people might even take it as a potential clue that Julie could be non-binary, because of how much we expect gender-matched pronouns at that point. (Not saying they should, just that they might.)