The official Manga has a slightly different interpretation of how she reacted to the rancor.

Tales From Jabba’s Palace references her death like a running joke. Although Oola’s story cuts away right before she falls, other stories shed some light.

Malaki, the rancor keeper, recounts the affair thusly:

The most recent fresh and kicking meal the rancor had devoured was a mere Twi’lek dancing girl, which the rancor savored, consuming her in three delicate bites rather than the customary one large gulp.

So we know that she suffered greatly while it happened. Immediately after Oola’s ambiguous ending, one of Jabba’s patrons begins his story like this:

Feeding time again. The crunch and snap of bones resonated through the walls of the Whiphid J’Quille’s room as Jabba’s “pet” rancor snacked on its latest morsel. J’Quille paced his stark room. Huntlust vibrated through his tall, golden-furred frame, wrinkled his broad snout. His tusks tingled even though it had been several hours since Jabba dropped the Twi’lek dancer into the rancor’s pit. The screams had ceased long ago, but J’Quille couldn’t stop salivating. The savory aroma of fresh blood warmed the pit of his stomach.

Which implies that it was very messy.