The man snatched her handbag before running off along Knarsdale Walk, Bedford, where the incident happened around lunchtime on September16.
The man is described as in his late teens, with light coloured hair.
Detective Constable Lisa Whitson, investigating, said: “This was a nasty incident which understandably has left the victim shaken, and we are working hard to find out who is responsible.
“This behaviour won’t be tolerated and we are urging anyone with information that could help us find the offender to get in touch. Anyone who was in the area at the time and saw the incident or knows who is responsible is asked to call us.”
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Anyone with information is asked to contact DC Whitson on 101 quoting crime reference JH/39760/17. Alternatively you can contact Crimestoppers anonymously on 0800 555 111.