Wanda Witter smiled this morning — a big, $100,000 smile.

After battling Social Security for years, the 80-year-old woman who was homeless until a week ago got one of the biggest I-told-you-so’s that a person can hope for.

“Ready?” asked the SunTrust bank teller, before spinning his monitor around to show Witter the new amount in her account on Tuesday morning.

She’d been checking with him almost daily (she won’t use an ATM machine), to see if she’d finally received the money owed to her.

On Tuesday — a day after I’d written about the former machinist from Corning, N.Y., in an article shared all over the world — the Social Security check for $99,999 showed up on that screen.

[‘I wasn’t crazy.’ A homeless woman’s long war to prove the feds owe her $100,000]

And Witter and the bank teller high-fived, smiled and laughed.

Because for 16 years, no one believed her. She called Social Security’s toll-free number, sent letters and tried to get someone to listen to her predicament. But most folks dismissed Witter as crazy as she roamed the nation’s capital with a hand-truck loaded down with three suitcases packed full of Social Security paperwork.

“Those papers,” she would tell people, “prove they owe me more than $100,000.”

They called her a hoarder and said that all those papers were a fire hazard. She slept in shelters and on the street. She didn’t trust anybody. And most counselors believed that mental illness, rather than messed up Social Security payments, were her problem.

Social worker Julie Turner believed her, though. Turner went through the neatly organized paperwork when they met in November and realized that it did, indeed, prove that Witter’s Social Security payments weren’t accurate. Then they stopped coming altogether when she had no fixed address and was homeless.

Witter then met attorney Daniela de la Piedra, who handles many Social Security disputes for the Legal Counsel for the Elderly, which is affiliated with the AARP.

And de la Piedra came to the same conclusion: Witter was owed a lot of money.

On Tuesday, Witter walked out of the bank, squinted at the sunlight and had to sit down on a bench.

“I”m overwhelmed. I’ve never had this much money before,” she said.

“How do you act when you have $100,000?” she wondered.

She decided to go buy some groceries, and take them to the apartment she moved into last week.

“You know, some sandwich meat, or something,” she said.

And she would take the bus home. Not a taxi.

“I’ve got to figure out what to do next and how to make the money last,” she said.

She’d like to go visit her four daughters, who all live in different states.

“I’ve got grandchildren I’ve never met,” she said.

The $99,999 payment was the most that Social Security could make as a lump sum, without an extended approval process. More is coming, her lawyer said.

And Witter is going to stay in D.C. until she gets all of it, she said.

In the meantime, she does have one big expense she’d like to get out of the way.

“My teeth,” she explained. “My top teeth. I want to smile without looking like an old hag. And I want implants. So dental work is what I want to figure out next.”

And no one doubts that she will.

Twitter: @petulad