Liam Payne's girlfriend left Argentina without the singer days before his death ... saying she didn't want to stay in one place too long -- and, bailed after a 5-day trip turned into 2 weeks.
Kate Cassidy -- a social media influencer based in Miami -- posted a video chronicling her journey back to the States from Buenos Aires on Monday ... 2 days before Liam fell to his death at the CasaSur Palermo Hotel.
Cassidy starts the clip by saying she's leaving the country because she doesn't like sticking around in one place too long ... saying she'd originally planned to stay 5 days, but she'd stuck around for about 2 weeks -- and, she just needed to go home.
Later on, KC mentions Liam in the clip ... saying she had to buy herself a neck pillow because -- while she usually travels with a Squishmallow -- she gave it to Liam, who wasn't with her.
The vid then gives fans an inside look at her trip back to the U.S. ... featuring the meal she ate and a quick overview of the flight, before ending up back at her home in Florida, where she slept in her own bed.
BTW ... many people online have noted Liam posted a video to his Snapchat just hours before his death. Kate's voice can be heard in the video -- obviously recorded earlier in their trip -- as Liam shows off his fancy digs down in the South American country.
As we've told you ... Liam fell to his death Wednesday afternoon -- and, according to 911 audio, Payne was in the midst of a meltdown in his third-floor hotel room before he fell.
The manager said a guest -- presumably Liam -- was "overwhelmed with drugs and alcohol" ... and, hotel staff was worried about his safety because they hadn't been able to enter the room for the previous few days.
Police are still investigating whether his fall was accidental or intentional.