Last month, Sarah Robinson made national headlines after she was caught stealing a few hundred dollars' worth of diapers, children's shoes and other items for her six children from a WalMart outside Kansas City, Missouri.

The police officer who responded didn't arrest Robinson, who said she was a widow, homeless and living in her car. Instead, he paid for the stuff himself and issued a minor ticket. Afterward, an outpouring of support left her with gift cards, food and thousands of dollars in donations.

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Friday, Robinson, 34, was arrested on federal methamphetamine charges out of Missouri, her lawyer in the theft case, David Langston, told NBC News on Sunday. The indictment, which was issued by a grand jury in March 2014, alleges that she possessed and intended to distribute the drug.

Langston didn't know any details about Robinson's drug case, and he isn't representing her, but he said that she may have been a peripheral player in a large meth operation and that the authorities could have arrested her as part of a legal strategy.

"They indict people at the fringe to strengthen the indictment," he said, noting that it's unlikely she would have spoken to reporters last month if she'd been a hardened drug dealer.

"My experience has been: if you're the target of a drug investigation, you don't want to draw the spotlight to you," he said.

Langston was among the people who was moved by Robinson's story last month — when he heard that she was trying to reuse diapers, he said, "it broke my heart" — so he decided to donate his services pro bono in her theft case. He didn't know much about Robinson's background, but he suspected that she had been living perilously close to homelessness before her husband died in a swimming accident a few years ago.

"There are people who find themselves in a desperate situation who do desperate things," Langston said. The accident may have been "the last straw," he said, adding, "These allegations may change people's minds."