I think the most natural interpretation is the following.
The mother has repeatedly said that she thinks her daughter is "bent on becoming" a "slut". That is, someone who (to quote from Clara's answer to the above linked question) is viewed as indecent and immoral by her neighbours.
The girl has just interjected into her mother's tirade, for only the second time in the entire text. The first time she spoke, she was protesting that, in spite of the way her mother was trying to portray her, she doesn't sing benna on Sundays - this was a way of trying to show that she's not bent on becoming someone indecent or immoral as her mother claimed. The second time, she asks what seems to be an innocent question - how can she feel the bread before buying it if the baker won't let her? The assumption behind her mother's response, I think (note that this is not backed up by cultural knowledge or any source I could find, just my presumption based on the text of the story itself), is that someone viewed by her neighbours as indecent or immoral or a "slut" would be someone that a baker would not let touch his bread - she might be seen as "dirty" and not a properly respected member of society, and perhaps other people wouldn't want to buy bread touched by a "dirty" person.
The more interesting part of your question is why the story finishes with this line. I have a few different thoughts about this, which don't necessarily contradict each other.
The very last clause is the first time the mother responds to her daughter (the girl's previous interjection having been ignored). Closing the story in this way, on a new type of interaction that we hadn't seen up till then, leaves it open how things will proceed from then on.
Maybe this clause precedes an explosion of rage from the mother, if she believes her daughter expects to be seen by the community as too "dirty" to touch bread. This would indicate that, given her mother's temperament, the girl should have kept her mouth shut or thought more carefully about how to phrase her question. This is a more pessimistic interpretation, the moral being that some people are so unreasonable that, even if you're close family, you can't even ask a simple question for fear of them twisting it around and putting words in your mouth.
On the other hand, a more optimistic interpretation would be that this is the start of the mother actually listening to her daughter. It's the first time she's shown any sign of hearing what her daughter said, after all. Perhaps the end of this story is the start of a more reasonable dialogue, wherein the girl convinces her mother that she's not bent on becoming someone indecent and immoral whom bakers wouldn't allow to touch their bread.
Either way, continuing the story after this point would change its style quite dramatically. As it stands, "Girl" is almost entirely a one-way monologue, with only two clauses from the second person in the scene. The moment where the mother actually responds to the daughter will surely mark a turning point, whether for good or bad, and a different type of conversation thereafter. It makes more sense to cut off the story before it becomes a true dialogue, thus making it a story that clearly portrays a mother who is talking and talking without paying much heed to what her daughter has to say.