In addition to the previous answer, which was great
Blanche had no choice but to avoid reality. How could she live with herself when the world she knew since she was little had just been removed from under her feet?
The world from where Blanche came was glamorous, enticing, and promising. She was the typical Southern Belle which would accept gentlemen callers, attend cotillions, and be treated like a princess.
She had it all- She married her teenage sweetheart, she was rich, she had an education, and a reputation for being a stunner.
Suddenly, her husband has a gay love affair behind her back, ends up committing suicide, lost her estate, her family became sick, Stella went off to marry a doubtful man and, Blanche was left behind.
She ended up re-building a woman from broken pieces, only she picked the worst pieces: Those pieces of her who are sexually invasive, co-dependent, alcoholic , and lost.
I think Blanche was already on the way to "Alysian Fields" the moment she set foot on the streetcar.