Answer: not exact, but the reason why Katie mentions Paris so often is probably where she was born. What it means to her may be family or culture.
Explanation:
I don’t know this story very well, but writers commonly use repetition to get a point out there. for example: in Danganronpa V3, Kokichi *constantly* lies, and everyone knows that. repetition can make the fact that he is a liar more clearer. with more analyzation, it could also get Kokichi’s view out there, especially HIS view on lying.
Apply this to Katie, she mentions Paris a lot. she talks about her family and certain events too, she even have souvenirs. We can infer that her parents were born in Paris, or that she was born there as well. What this means to her is that Paris symbolizes family to her.
This is just my interpretation though!