The daughter of Frankel was a clear-cut four-and-a-half-length victor in the Cheshire Oaks on Wednesday, but she is not currently entered for the Epsom feature on May 31.
However, Gosden believes owner Emirates Park Pty Ltd, whose principal is Nasser Lootah, will stump up the necessary £30,000 to add her to the race at the five-day stage.
The trainer said: “I talked to the owner and he is very keen to do so (supplement her for the Oaks). It is my fault for not putting her in.
“It’s not easy to do it off one run on the all-weather, but I’m sure she will be supplemented.”
Mehdaayih is a general 5-1 chance for the Oaks.