Okay, hear me out.. Beatrice is the Baudelaire's mom.
Count olaf pushed Beatrice, but, she survived. How? The dragon fly costume.
You can see Kit use the dragon fly costume to survive a fall in the mountain episode. (Forgot the name). So why couldn't Beatrice do it aswell?
We also hear the woman with hair but no beard and the man with a beard but no hair say Count Olaf *tried* to kill Beatrice. Which leaves a possibility he failed.
And, The fact there are three Beatrice's just leaves more evidence. The Baudelaire's mom, Lemony Snicket's Beatrice, and the child.
She could of fell for their father, and died in the fire. Because she didn't die by being pushed, because one of the "Dear Beatrice" notes at the beginning of each episode said something about her house not being able to be put out.
Why didn't she tell Lemony? She fell for the Baudelaire's father. Hey.. Better letting someone think you died loving them than lived and fell for another man.. Right?
But that's just a theory.. An unfortunate theory!