Yeah, you can't use here word by word translation because "beef" already means "ox meat"... You could try this, but, for this, english already offers this specific word "beef"... This comes from the time of Norman Court in England, when farmers used english word with germanic origin for "ox" (compare, for example, with German "Ochse"), but noble people from the normand court used the french word "boeuf" (bœuf), from latin "bove", which gave origin to "beef". As they used to eat the meat of the "boeuf", "beef" came to mean it, the "meat of the ox"!! Sorry if the explanation is not so clear... :)

If you want to be literal you would say, "The girl eats meat of beef". Which is certainly too literal. :)