Beth won the biggest prize, described as a higher medal than Jamie's, which we've been told was a silver medal.
Roberta and Michele both won bronze medals, which are lower ranking medals than silver.
Beth is also described as having competed more times than Roberta who has competed seven times.
Jamie is described as having competed fewer times than Roberta, and Michele has competed three times.
Therefore, Beth has competed more times than the others and has won the biggest prize to date.