There's rare chance Siren to Enter your Spawn Room, it happen if Siren see you in the room, so i suggestion hide on the right side of the corner in case she try to enter.

Which Room/Location :
go left after you leave your spawn room, then on intersection go to the right,
Intersection then go straight then go to the room on the left,


there's small spot that u can hide from siren's hitbox u will safe in there.

Which Room/Location : After leaving your spawn room, go to the left, intersection go to the right

then Intersection, got the left, go to the rooms on the left


after entering the room there's spot where siren's hitbox will not detect you, it's on the left spot or infront of "secret exit door" in Hard Mode Ending.

Third Siren Will Spawn After Second Siren got her second buff (faster movement)
The Costume Third Siren use depend costume that you already unlocked for her.

but Third Siren Cutscene Will not be added in Extra