In the scene where Mrs. Howell sees that Eva looks like Ginger, she tries to think of what the French would say & then states, "I don't speak French." Although, in #2.17; You've Been Disconnected, she states that she speaks FLUENT French & Italian. She is also heard using French on several other episodes.
At the farewell party Mrs. Howell gives Eva a diamond necklace. Eva fiddles around with it trying to find the clasp. In the immediate shot, she's wearing the necklace without having fastened it.
The Skipper says the boat won't turn over when he tries to start it. It turns over but it won't start.
Just after her transformation, Eva looks at herself in the mirror with her back to the camera. Her image is reflected in the mirror with Ginger standing to her right. At one point, the image in the mirror shakes her head, but Eva does not.
When Eva lures Ginger into the jungle to overpower her, the line "Why did you bring me all the way out here?" is clearly not dubbed by Tina Louise.
Eva gave the boat key to Skipper to keep if they agree to leave her alone on the island. When he tries the key and the boat won't start, Eva admits to burying the spark plugs where they can't be found. As Eva can't now be trusted, it makes no sense that the castaways would give the key back to her, leaving her with the key and the whereabouts of the spark plugs.