There are some similarities here, especially the eyes. The hair is different, however. She may have grown it longer and straightened it. I don't know...
The girl in Alcala's photo looks older than 15 to me. There are no details available of the circumstances of Luray's disappearance, other than "she may have traveled out of the area with an adult male". Was she a runaway?
Where was Alcala in August, 1964? The timeline I've seen has him in the Army between 1961-64, and then nothing until his graduation from UCLA in 1968.