The term "literary devices" is quite broad and can be divided into two categories: literary elements and literary techniques. Let's talk about both types of literary devices so that you can have everything covered.
First, we need to speak about literary elements (with a focus on theme). These things are basically "required" by authors to be used in some kind of professional way in order to tell their story. Yes, Grace uses plot & setting & dialogue & mood very well. The story's rising action begins as the girls enter Jane's house. But let's talk specifically about the protagonist which, here, is actually Rose. She is set against the antagonist: Jane. It is Hera who is the narrator. The conflict here is between the protagonist vs. the antagonist. Specifically it is Rose vs. Jane, or more generally it is Maori vs. Pakeha.
The last (and possibly the most important) literary element here is theme. The main theme of "A Way of Talking" is one of racial discrimination against native peoples and, specifically, the New Zealand Maori. (Although, I must say, I find it ironic that there is also discrimination against the Pakeha!) In my opinion, a good quotation to exemplify the theme is as follows:
And how can the likes of Jane know when we go around pretending all is well. How can Jane know us?
This is Rose's reasoning as to why she is abrasive towards Jane. It's a perfect example of the theme of racial discrimination.
Patricia Grace also uses quite a few literary techniques to heighten her reader's appreciation. The two that jump out at me the most are imagery, hyperbole, and metaphor. In regards to imagery, just look at how Jane's house is described! There is no doubt that she is "Pakeha"! In regards to hyperbole, Patricia Grace uses the character of Rose to employ this literary technique. My favorite example of this is when Rose parades around the house pretending to walk like Jane (in a derogatory fashion, of course), talk in a "Pakehafied" way, and spouting remarks of condescension to the Maori.
This leads perfectly into the next literary technique: metaphor. There is a very important one in regards to Rose and her hyperbole. Rose constantly refers to Jane as having a "thick hide" or a "tough hide." That is the metaphor here. Even though Jane doesn't have any thicker skin than anyone else, the term "thick hide" is a metaphor that means Jane can take quite a bit from the Maori population, especially when they bring her business. In fact, Rose uses this metaphor as the main reason to explain why Jane won't hold Rose's abrasive comments (such as, "Do these Maori have names?") against the family.
Thus, as you can see, Patricia Grace uses many literary devices in her story "A Way of Talking" in the form of both literary elements and literary techniques.