The court was told Elen Humphreys, 25, of Garndolbenmaen used the insult against Angela Payne when she went to Payne's house to collect some of her father's belongings, The Daily Telegraph reported Monday.
"Leave well alone, you English cow," Humphreys was accused of saying to Payne.
Andrew Hutchinson, Humphreys' attorney, said his client had been under stress because she had just discovered her father had been going "backwards and forwards" between Payne and Humphreys' mother, to whom he had been married for 32 years.
"Emotions were running high," Hutchinson said.
Humphreys was sentenced to a 12-month conditional release and was ordered to pay $77.48 in compensation to Payne.