The prince allegedly sent the letters to Welsh-born Janet Jenkins, reports Contactmusic.
One of the six letters to Jenkins was penned in 1980, just a year before he tied the knot with Princess Diana, reports the Sun.
Charles and Jenkins met in 1975 when she was a receptionist at the British consulate in Montreal, Canada.
Los Angeles woman Alicia Carroll claims that Jenkins, now 63, sold her the letters.
Jenkins insists that Carroll told her she wanted to display the letters in a museum.
However, Jenkins is demanding the letters' return after learning that Carroll has actually put them on eBay for 30,000 dollars.