I think you are being overprotective here OP. I get it; I understand the mindset of "if she doesn't do it then there is zero risk" rather than contemplate the slight risk of what you anticipate happening. Thing is, if we lived like that we'd never do anything.
I've said before; allowing kids to do things isn't about being reckless, it is about assessing risk sensibly and preparing kids to deal with things.
Look at the facts of the situation. You are in a Marriott - arguably a very decent hotel which will have CCTV EVERYWHERE and security actively watching the security cameras as well. It's not just a case of there being cameras and they look at them later; many hotels, particularly the nicer ones, have active security monitoring things.
In order for someone to grab your DD as you say, they would have to be glued to their hotel door at that very moment waiting for your DD to walk past alone. Remember - possible is not the same as probable, and this, while POSSIBLE (albeit very remotely), it is definitely not PROBABLE.
The other scenario is someone on that corridor returning to their room and pulling her in but again, the likelihood of that very person at that very moment deciding to attempt to abduct an unwilling child in full view of cameras is extremely slim.
Presumably you have prepared your DD for encountering strangers and have taught her to scream blue bloody murder and kick off if someone tries to grab her. In a hotel corridor like that, a girl screaming and going off it is definitely going to attract a LOT of attention - something a potential abductor will NOT want. If she is carrying a bin then that will in all likelihood be dropped on the spot (thus identifying the room she has been dragged into) or even swung at the attacker causing even more commotion/noise etc. It's too much hassle/risk for any would-be abductor.
So add up the facts to consider the risk: it is a short walk down a corridor in a decent hotel which has security and that corridor will be monitored by CCTV which would immediately pick up someone grabbing your DD - so in the highly unlikely event it happened, it would be seen. Should it happen, your DD would, I presume, kick off and so there would be enough noise and commotion that a would-be abductor wouldn't likely select that type of location/environment as an ideal spot. Plus, you would likely notice within seconds that she was not back so there is a very very limited window for any abductor to "vanish" your DD - she would be found almost immediately.
If you are that bothered stand at your hotel door or leave it open so you can hear any commotion. But tbh, I DO think you are catastrophising here. You cannot prevent everything in life. Trafficking happens just as much here as in the USA. Don't teach your child to be scared of everything just because it is another country. I see nothing wrong with your DD carrying out this task.