Some dictionaries say "show up" and "turn up" are synonym, but according to my study:
show up: is used to mean to arrive when people are waiting for you expectedly.
- Seth showed up, apologising for being late.
turn up: is used to mean to arrive in a way that is unexpected
She turned up at my house late one night.
So, it is more meaningful to say "She just turned up unannounced on my doorstep." than "She just showed up unannounced on my doorstep."
But a woman in the film "Upgraded 2024." said "you can't just showed up unannounced".
show up
: informal to arrive, especially at the place where someone is waiting for youturn up
: to arrive or appear somewhere, usually unexpectedly or in a way that was not planned Those words mean that the meanings given are for some, but not all usages. 'Show up' and 'turn up' can both mean to arrive expectedly or unexpectedly.