Mum-of-two Natasha Clegg, 32, is believed to have boarded a train on Tuesday at around 8.30am after leaving her Barnsley home.
She is now believed to be in the Leeds area.
Her mum Michelle Thompson said Natasha's two children are 'heartbroken'.
She added: "We just need her home where she belongs with her babies."
Michelle thanked members of the public who had been out looking for Natasha.
South Yorkshire Police have launched a missing persons investigation.
Anyone with information should contact the force quoting incident number is 415 of 10 December 2019.