What lead Blanche to her final break down?

In the play "A Streetcar Named Desire" Blanche ends up
being institutionalized in a mental ward. Many things lead to her final
breakdown.

Perhaps the most prominent thing which led to
her breakdown was Stanley's rape of Blanche. The sexual tension between both Stanley and
Blanche built throughout the entire play. Blanche would display herself in front of him
as a taunt.

Another thing which lead to Blanche's breakdown
was the fact that Mitch decides to leave her. Mitch admits that there were certain
things about Blanche which he knew she had shaded (a reference to the lamps and
coverings she placed over them to disguise her age), he could not forgive her for lying
to him about her prostituting past.

The final nail in
Blanche's figurative coffin was the fact that Stella had left her once again. Blanche
never forgave Stella for leaving their childhood home. Blanche even blames Stella for
losing Belle Reve- though she had nothing to do with it. Blanche destroyed Belle Reve in
the same way which her family had- trying to use it to support them
financially.

In the end, Stella decides to choose Stanley
over Blanche. This decision propels Blanche over the edge.