If Blanche had married Harry in the first episode The Engagement, what do you think would have happened to Rose and Dorothy? Would they live somewhere else together or just be out on the street, since Rose said they couldn't afford a house and that she and Dorothy would become bag ladies? Could that have been part of the reason why she wanted to stop the wedding?

Could have been part of it- but she also had a bad feeling about him. And she was right. :)