It occurs to me that the censored bar covers up the location of the staking wound.
How do we know if she actually hit the heart?

Maybe Bloody Mary has gotten very good at playing dead from countless near stakings in her past.

(this could also be why vampires are afraid of crucifixes. You would flinch too, if you had these things shoved in your face for decades.)

And, as you have noted, the stake really doesn't "kill" the vampire. It just keeps it stuck in place. So, someone later dislodges it, and blam, she's back. (or maybe, on the other side of town, someone is starting to make bloody marys... 3x a charm)

Of course, we could get the monologue... "You think you have defeated me...."