Here is the Prayer from the Mass for her feast day which I found in my Dad's Missal:
"O God, who on the summit of Mount Sinai didst give the Law to Moses, and didst by means of Thy holy angels miraculously place the body of Blessed Katherine, Thy Virgin and Martyr, grant we beseech Thee, that through her merits and intercession we may be able to reach that mountain which is Christ."
The Monastery of St. Katherine at Sinai