It wouldn't have occurred to me to call twee a foreign word. However, my feeling of its meaning was... very close to the gloss given on wiktionary (and marked "UK"):
>> Overly quaint, dainty, cute or nice.
The unambiguously American Merriam-Webster agrees:
>> affectedly or excessively dainty, delicate, cute, or quaint
"Characteristic of theater kids" conveys something different to me. Do you disagree with the dictionary gloss, or do you think it's a good description of how people might describe a performance by theater kids?
https://www.edwest.co.uk/p/the-unstoppable-rise-of-british-t...
(nb I'm not sure about the political analysis here but the citations are good.)