First the ancestral plant must have adapted to move its tentacles and leaves in a particular direction, giving it a greater chance of sticking to and engulfing a passing insect.
Next it sped up how quickly it detected prey and tried to respond.
Then the plant would have had to find a way to become selective, so it only tried to trap live prey and not any detritus that landed upon it.
Finally, it must have evolved its tentacles into sensory hairs and teeth that detect and wrap around prey, respectively, while also losing its sticky glands and growing new digestive glands capable of digesting the victim's corpse.
The adaptations led to the plant's ability to eat larger insects for more nutrition. Link -via the Presurfer
either God created the carnivorous plant before the Fall, meaning there WAS death before the Fall (goes against dogma)
OR after the Fall, the plant dramatically changed from being a plant that did not consume animal matter to one that did - in LESS time than evolution took to do so. So what would you call the rapid adaptation of existing body structures to new purposes but evolution?
Regarding bug-eating plants in the garden of eden: This is somewhat speculative as well, but I think there is some question whether flies would have been considered "alive" at that time. The Bible refers to the "breath" in connection with life. Like plants, insects don't really "breathe" the way other animals do. Just one possible explanation.
(oh, and Misc - it wouldn't, not unless some random mutation caused it to stop producing the sticky fluid, and the new breed flourished more. This is why humans still have apendix and other species other useless things).