|[All images from residentevil.wikia.com]|
The outfit works.
Not realistic, the mini-skirt/tube top costuming of Resident Evil 3's Jill Valentine helps stress the already uncomfortable sexuality of the series to maximum heights.
It's ridiculous that any human being might try to escape a monster-infested city in that get up, of course, but realism is not for fictional mediums. Jill's outfit tells us, as any good character design should, information about both the character and the game it is in.