ABERDEEN, S.D. - One might think a wedding dress being given away would have a sad story behind it.

Not this one.

After getting married last year, Allisa Gross of Aberdeen knows all the work and money it takes to put together a wedding. So when her sister, Savanna Nelson, said she was ready to get married, Gross wanted to help.

"It's probably a good idea to put in some extra effort, because these are a lot of work," Gross said.

Nelson got engaged earlier this year and started the wedding planning process in Minnesota, Gross said. From five hours away, Gross was helping any way she could, including scouting the rummage sale pages on Facebook, which is where she saw a unique post.

Someone was giving away a wedding dress — very explicitly giving it away, and not selling it.

"When she said it was free, I just assumed that she must have gone and got married," Gross said.

That person was Sierra Bivens, who is not married.

"For the summers, I would go down and clean with my sister in Tennessee, and we were cleaning a house one time and this lady was like, 'What size are you?' and I told her," Bivens said.

The woman bought two wedding dresses for her daughter, and a mermaid-cut size 12 David's Bridal number didn't make the cut. So the woman offered it to Bivens, who had just graduated from high school. That was summer 2014.

"She's like, 'You're young, you'll find somebody,' and I'm like, 'OK,'" said Bivens, now 22.

There was one stipulation with taking the dress.

"The lady made me promise since she had given it to me, that if I ever didn't need it to give it away," Bivens said.

In fall, Bivens realized she wasn't getting married anytime soon.

"I am dating somebody, and we have talked about that, but he said that we're not going to be getting married for a long time," she said.

A Langford resident, Bivens graduated from Northern State University in spring and moved back home for the time being, carpooling to her job at Avera St. Luke's Hospital with her mom, who works in the sewing shop above Brides 'N' Belles.

"She gets to see dresses and work on dresses all the time," Bivens said.

She worried the dress would go out of style sooner rather than later, and it didn't fit her anymore anyway.

"You never really know until you try something on," Bivens said. "It was something I had considered."

So she handed off the dress to Gross last week.

Nelson won't get to see it in person or try it on until Gross heads east for Christmas later this month. Hopefully, her sister likes the dress, Gross said, and will continue to plan a party for her wedding, rather than just a meeting at the local courthouse.

"Anybody that asks to help — absolutely. Remember them and ask them when you need help," Gross said of planning a wedding. "If they offer help, don't forget them."