Amelia wasn't really an elder

She was trapped in a tight confined space with lycans on all sides. Even a skilled warrior would eventually go down when they don't have room to fight and are greatly outnumbered. She also may have gone soft over the years. In the prologue of the sequel, she looked like a pretty badass warrior, but in this movie she looked kind of... dainty. Her fighting skills probably went rusty after not having been in the field for centuries.

I didn't read the book but apparently it says Amelia killed quite a few Lycans before being overwhelmed from the sheer number of attackers. Also the elders are roughly 1600 years old I think. According to websites that recount their leapfrog technique. :)