tbf Tolkien himself tries to explain it as a mixture of desperation and loyalty to Frodo, a super elven sword and the spider impaling herself in an ill-fated attacking move. Doesn't really come across in the film. :)

I'm not sure where good storytelling comes into men in films dodging bullets and beating up dozens of assailants or why the stylised violence suddenly becomes less believable because the person winning against improbable odds is female though. Or where the Tolkein original plotline involving a woman with a broken arm defeating a Nazgûl lord so strong it's prophecied no man can kill him in a swordfight fits into woke propaganda trends :D