Why doesnt Frieda want to go to Isaley's? Where does she want to go instead?

Frieda didn't want ice-cream, she wanted potato chips. Thus, she was to go to Miss. Bertha's because she had potato chips, and she had them for free.

 “I don’t want ice cream. I want potato chips.”
“They got potato chips at Isaley’s.”
“I know, but why go all that long way? Miss Bertha got potato chips.”