A member of  RNLI Kinghorn Lifeboat crew jumped into the water to rescue her after she was found clinging to the back of the boat south of Inchkeith Island on Saturday morning.
It is thought she had been in the water for up to half an hour and was in the early stages of hypothermia.
She had been on the boat with a man and a nine-year-old girl.
The lifeboat took the woman and the girl to shore, escorted by a Police Scotland boat which was working in the area, and both were taken to hospital by ambulance as a precaution.
Lifeboat Helmsman Scott McIlravie said: "Communications between us and the casualty were difficult, although they thankfully had a VHF radio on board so we were able to use our direction finding equipment to quickly locate the boat which was around half a mile south of the island.
"We quickly assessed the situation on arrival and found a female in the water clinging to the back of the dinghy. One of our team jumped into the water to get hold of her, and she was then brought to safety on the lifeboat.
"The second crew member on the boat was a young girl and she was also taken onto the lifeboat to be taken back to Kinghorn where an ambulance was waiting to assess both casualties.
"Both casualties were cold and distressed, with the woman who had been in the water suffering from the early stages of hypothermia."
He added: "It was fortunate that this vessel had a VHF radio on board today.
"There was very little chance that the woman would have got back onboard the dinghy today without third party assistance.
"Since the vessel was able to call for assistance immediately, and we were then able to find the boat quickly, this lady fortunately had a very lucky escape."
All three people on board the sailing boat were wearing life jackets.
A woman has been pulled to safety after falling overboard from a dinghy in the Firth of Forth.