Dyfed-Powys Police said the woman was killed in the countryside near the village of Guilsfield on September 1.
She is said to have been walking her dogs on a public path past a field of 40 cows when she was killed.
The Health and Safety Executive (HSE) have been informed and are making enquiries, a spokesman said.
HSE figures show that 32 people have been killed by cows between 2018 and 2022, accounting for a fifth of all deaths in the agriculture, forestry and fishing industry. However, the HSE have stressed that members of the public are rarely killed by cattle.
Earlier this year, an inquest heard how telecoms worker Michael Holmes and his wife were trampled by a herd of cows during a lunchtime walk in lockdown in Netherton, West Yorkshire.
The couple had been walking their daughter’s two whippet dogs, who were both on leads, when they were charged at by a herd of between 25 to 30 cows and their calves.
The National Farmers Union (NFU) have suggested that walkers should stay safe by following the Countryside Code, which recommends keeping dogs on a lead to prevent them from coming between a cow and its calf.
The organisation has previously campaigned for legal permission to allow farmers to divert public rights of way where cattle are present, but this has been opposed by walking groups.
Stuart Roberts, the deputy chairman of the NFU, has also urged members of the public not to run away from cows.
“Don’t run away. It’s almost counterintuitive but the best thing is to move slowly, steadily. If you run, they may chase you.”
Farmers can face prosecution if their cattle maul walkers or farm workers.
The Ramblers Association recommends that walkers avoid getting between cows and their calves and move quietly and quickly. Dogs should be kept on a short lead and under effective control.