But instead it has left the normally bubbly 17-year-old smouldering with anger. For, following a local tradition that seems extraordinary in a country which has elected its first black president, there was not just one formal dance for the 54 classmates who graduated from Montgomery County High, but two.
On the first night, a prom was held for the school's white students; the following night came the celebration for Miss Nobles and the school's other blacks.
In early summer when Georgia peaches are at their sweetest and high school seniors can't wait to be loosed on the world, separate proms are part of the bitter aftertaste of segregation that persists in parts of America's Deep South.
For nearly 40 years state school pupils have been educated together. They have played sports together and developed close bonds of friendship, before finding themselves face to face with a cruel ghost from America's past.
"It was heartbreaking," said Miss Nobles, who will be leaving home to go to university this autumn. "It was the one night to see all your friends dressed up and I'm told, I have to wait until the next night because of the colour of my skin."
The annual prom held by high schools across America near the end of the academic year is big event, for which students and parents spend months preparing. But in a handful of Southern towns, parents still insist on whites-only proms which blacks are not allowed to attend.
The election of Barack Obama did nothing to change attitudes that go back generations in the small rural towns of Montgomery county, Georgia; the surge of pride black people felt in the election of the first black President was met by frosty silence by whites. The county, which is two thirds white, voted overwhelmingly Republican last November and attitudes have hardened as the months have passed.
Barred from attending the white prom, Kera still stood outside to show moral support for her closest friends, cheering and taking photographs as they arrived and did the "senior walk" into the community hall with their boyfriends or their fathers. Then she left, with her black friends.
Next evening her own white friends encouraged her and took their own pictures as she and her friends dressed in lavishly coloured dresses and rented dress suits for their own event at the same venue.
She was close to tears. "Every (school) class we sat beside each other," she said, ticking off the names of her best white girlfirends, Harley Boone and Cierra Sharpe.
"We love each other. But there's a lot of hidden history here, and while everybody gets along there's always something... If your parents are a certain way nine times out of 10 you're going to think the same way."
Blake Conner, 17, who is white, did not want to go to the prom at all, but was persuaded to attend by friends. "There's a lot of people I went to school with, who are my friends that I wish could have been there," he said, lifting sacks of sweet corn from an elderly farmer's pickup truck into farm shop where he has a summer job.
He believes it would be hard to have a successful integrated prom for what he calls "cultural reasons."
"My friends tried to organise a joint prom but they just couldn't agree on the music or even a theme," he said.
For two white sisters, Terra and Tamara Fountain, both of whom have black boyfriends, prom night was especially trying. "I wanted to go to the black prom," said Terra, 18, "but my mom wouldn't pay. She doesn't like me talking to black people anyway." She now lives with her black boyfriend, Gary Carswell, but neither feels comfortable living under scrutiny in a small town.
Her sister Tamara, 16, added that she cannot be seen on the street with her boyfriend Ken Troupe. "Its terrible, everybody's so racist round here," she said. "If they see you in public with a black guy they just stare at you with hate in their eyes."
Montgomery county's time warp seems to be rooted in institutionalised racism. Until relatively recently the black community of this town lived in terror of the lynch mob.
In one infamous killing in early August 1930, a prominent 70-year old black politician was taken from his house by a mob and tortured to death. In 1944, after a one-day trial by an all white jury, a maid was convicted and later executed for shooting dead a man who was sexually assaulting her.
Racially motivated killings continued through the 1950s, and in the late 1970s a white man was shot dead for having an affair with a black woman. No one was prosecuted.
Officials insist that the once powerful Ku Klux Klan is no longer active. "The Klan is now history and thank the Lord for that," said one. "They are gone now, we are just dealing with some old attitudes."
It's those attitudes that kept last month's proms segregated, since the parents of white pupils refuse to support it another way. This year's "white folks' prom", as it is known, was a lavish affair for which tickets cost over $200 a head - out of the reach of most black pupils, who are from some of the poorest families in the country.
The sadness of the black pupils was captured by Gillian Laub, a freelance photographer who reported on the town's segregated events for the New York Times Magazine.
Harley Boone, a graduating white student who posed by her parents' outdoor swimming pool, told her: "There's always been two separate proms. It don't seem like a big deal around here, it's just what we know and what our parents have done for so many years.
"In our school system it's not really about being racist or having all white friends or all black friends. We all hang out together, we're all in the same classes, and we all eat lunch together at the same table. It's not about what colour you are."
Miss Boone's comments outraged many and she found herself cruelly caricatured as a racist on a YouTube video that has been widely viewed.
Betty McCoy, the editor of the local newspaper, the Montgomery Monitor, has watched with dismay as segregated proms continue year after year. "It's really the fault of a few families," she said. "This is really a friendly and well integrated community."
Pastor F Lee Carter of the African Baptist Church - who once marched for civil rights in Selma, Alabama with Rev Martin Luther King, has little patience with those who demand separate proms.
"Political life is intertwined; educational life is too," he said. "So why shouldn't our social life be intertwined as well?"
But the school superintendent, Leon Batten, pointed out: "The most segregated hour of the week is 11 am on a Sunday morning when white and black attend separate churches."
Even so, Mr Batten has decided it is time to end the segregation - and next year there will be an integrated prom, arranged by the school instead of the parents, he told The Sunday Telegraph. "It may not be a great success at first, but we will persist and over time the segregation will be history."