Is there any way to prevent a siren from putting you to sleep? I'd say out of everything that's killed me, that's the most annoying. BESIDES JUST STANDING AWAY FROM IT
Throwing weapons, teleporting, buddies, traps, high dex, maybe high will (idk if it works that way, but it makes sense), praying to dulcius or zapping her. Use everything, be creative.
EDIT: Lots of weak buddies, for the call of a siren easily overwhelms a single strong entity, but many weak targets will make quick work of a siren.