There are a number of different aspects that we could comment on when we think about the title of this excellent text and how it relates to the content. Firstly, "Girl" clearly indicates the receiver of the diatribe or advice that the mother figure gives to her daughter. When we think of the word "girl," we think of a young girl who is in need of advice and guidance from a mother figure. This certainly would appear to be the case, as the text basically contains a non-stop flow of suggestions from the mother to the daughter.
But at the same time, the word "girl" can also be used as an insult to suggest that the woman is much younger and more immature than she actually is. There is a sense in which the title also captures this idea, as the mother, in seeking to give her daughter lots of advice, actually appears to be incredibly insulting at times, such as when she interprets one of the few things that her daughter says as sluttish behaviour that would make her a "loose" woman:
...but what if the baker won't let me feel the bread?; you mean to say that after all you are really going to be the kind of woman who the baker won't let near the bread?
The mother is trying to teach her daughter sexual norms so that she will not be regarded as a slut. Her quick response to an interjection made by her daughter that could have been uttered out of frustration illustrates this more insulting and patronising meaning of the title.
Lastly, you could argue that the title reflects a lot about the relationship between the mother and daughter. The text contains a non-stop list of suggestions that is seemingly without end, yet never does the mother give her daughter any encouragement or soft words. It appears the title is relevant to the relationship because the mother is not bringing up her daughter to be a woman in the way that she would be. The non-stop criticism and advice keeps her daughter in the place of being a "girl" rather than instilling her with self-confidence so that she can grow up and be a woman.