Delia has changed over time as:
"She has become much bolder, like Bertha".
<u>Explanation:</u>
Delia has undergone tremendous abuse, mental and physical, through the hand of her husband, Sykes.
Even though she is the sole money earner for the household, doing hard labor work, Sykes takes no notice of the same and keeps abusing, humiliating and degrading her. Delia is otherwise a hardworking and a non-violent woman, who even after going through so much pain by the hands of Sykes, does not revolt or back answers him.
However, in one instance, after many years of repeated violence, she back answers Sykes, and also attempts to hit him with a rod which she catches hold of in their house. This surprises Sykes and makes him rush out of the house and makes him think about what Delia just did.
Hence, Delia took this step after many years of her marriage, indicating that she has become bolder, like Bertha (Sykes's Mistress), over time.