Karime Macías, the wife of disgraced Mexican politician Javier Duarte, was arrested in London on Tuesday.
Mexico has requested the extradition of Ms Macías, 43, for alleged misuse of funds from a social welfare programme.
She was released on bail after six hours and told not to leave London pending an extradition hearing.
Her husband, the former governor of Veracruz province, is serving a nine-year sentence in jail after he pleaded guilty to embezzling public funds.
'I deserve abundance'
Mr Duarte was dubbed "the worst governor in history" and there remains much anger in his home state that his sentence was not more severe.
Ms Macías hit the headlines in Mexico when a notebook believed to belong to her was found during a search of the couple's home.
In it, the sentence "I deserve abundance" had been written over and over again.
Prosecutors in Mexico say she is suspected of siphoning off 112 million pesos ($5.9m; £4.6m) from a welfare fund for families in Veracruz.
Her lawyer, Marco Antonio del Toro, said that she had voluntarily handed herself in to police in London on Tuesday. Mr del Toro also said that his client had requested political asylum in the UK "following rights abuses committed since Javier Duarte was arrested".
The governor who succeeded Mr Duarte in office in Veracruz, Miguel Ángel Yunes Linares, said in May 2018 that he had information that Ms Macías was in London, allegedly living a life of luxury in a flat in Belgravia and spending £60,000 ($77,000) a month.
Javier Duarte later confirmed in an interview that his wife was residing in London with their three children.
Who is Javier Duarte?
Mr Duarte was governor of the eastern state of Veracruz from 2010 to 2016. He resigned from his post just 45 days before the end of his tenure in order "to clear his name" after being accused of corruption, money laundering and involvement in organised crime.
He disappeared shortly after his resignation and was arrested six months later in Guatemala in a joint operation between Interpol and Guatemalan police.
During a search of his luxury ranch in Mexico, police also found 17 paintings believed to be by famous artists such as Joan Miró, Fernando Botero and Leonora Carrington.
There was an upsurge in violence and corruption in the state during his six years in office, in particular a spike in the number of murders and disappearances.
Under Mr Duarte, Veracruz also became the most dangerous region of the country for journalists, with 17 killed during his term.