In Fahrenheit 451 by Ray Bradbury, what did Mildred regret losing in the fire?
At the beginning of Part Three, Montag is forced to burn his own home as a punishment for the illegal possession of books. For Mildred, losing her home is not just about losing her security, it also causes her to lose her 'family,' as we see from the text:
She shoved the valise in the waiting beetle, climbed in, and sat mumbling, "Poor family, poor family, oh everything gone, everything, everything gone now ...."
For Mildred, then, she is most upset about losing access to the 'family' and losing her material possessions. That she values these things so highly reveals much about her character: she is superficial and shallow and only interested in the world of entertainment. Moreover, she values these things above human relationships, even her marriage.
Mildred believes that books have brought nothing but misery to her life and it was for this reason that she reported her husband's book collection to the authorities in the first place.
Montag's wife Mildred certainly shows her true colors when she turns her own husband in for having and reading books. She throws him to the authorities in an effort to save her own skin. This is tragic and selfish in and of itself, but when the firemen show up at her house with Montag, she doesn't even acknowledge him. She walks out of the house before it is burned and is overheard saying to herself, "Poor family, poor family, oh everything gone, everything, everything gone now" (114). The family Mildred is grieving for is not anyone real or anyone from her own family. The family is people on TV that Mildred loyally watches every day. She proves by her behavior that she is more involved in the lives of characters in a fictitious story than her husband's life. Montag then watches as his wife gets into a taxi and drives away without another word.
Not surprisingly, given who she is, all Millie cares about is the parlour walls.
Throughout the book, we see that Millie is totally wrapped up in the "family" that she has in the parlour walls. She wants to get a new fourth wall so that she can be even more obsessed with them. She spends all her time with them.
On the night that she calls in the alarm, she walks out past Guy Montag and gets in a taxi. All he can hear from her is some mumbling about her "family."