Although they have been friends nearly all their lives, Hilly and Skeeter represent quite different perspectives about social justice—and that is the source of their conflict.
Skeeter is not stuck in the traditional ways of racial discrimination that abound in their hometown of Jackson, Mississippi. Through her loving relationship with Constantine during her formative years and now through an open relationship with Aibileen as she begins collecting stories for publication, Skeeter becomes an advocate for civil rights in her community.
Hilly, on the other hand, represents the traditional and very segregated views which dominated upper-class white society during this time in the South—and maybe especially in Jackson, Mississippi. Hilly wants her black maid to do most of the household work for her so that she is free for ongoing social engagements. While her "help" cleans her dishes and prepares her food, she doesn't want them sharing her bathroom and makes it her personal mission to ensure that each family in Jackson builds a separate restroom for their black maids to use. In a great (and humorous) act of defiance toward this belief, Skeeter covers Hilly's lawn in toilets as a practical joke, which fairly solidifies the conflict between the two former friends.
Interestingly, Hilly tries to convince the town (and maybe herself) that she is not racist through her fundraising efforts:
“Hilly.” I just need to hear her say it. “Just who is all that pound cake money being raised for, anyway?”
She rolls her eyes. “The Poor Starving Children of Africa?”
I wait for her to catch the irony of this, that she’ll send money to colored people overseas, but not across town.
Unfortunately, Hilly does not see the irony in this situation and furthers her stance by clarifying why they must send actual food and not money to Africa:
You cannot give these tribal people money ... There is no Jitney 14 Grocery in the Ogaden Desert. And how would we even know if they're even feeding their kids with it? They're likely to go to the local voodoo tent and get a satanic tattoo with our money.
Hilly thus is symbolic of the traditionally racist views of Jackson during this era, and Skeeter is symbolic of progressive actions, bringing to light the ways upper-class white women have taken advantage of their black maids and trying to ignite change. The two are positioned for conflict because of their polar opposite views on civil rights.