a cross between Morticia from The Addams F amily and a lemon

The expression "a cross between" sets up a descriptive phrase in which two different characteristics are combined. In this case, they are referring to a character, Morticia Addams, who has been portrayed on television by Carolyn Jones, and in motion pictures by Angelica Houston. A lemon is often used to refer to something sour--this is a somewhat clumsy use of the "a cross between" locution, because she is referring to her appearance, and lemons only appear to be yellow.

However, i suspect she uses lemon to mean sour. So, i would say that she refers to Angelica Houston in her role as Morticia Addams . . .



. . . and the expression someone makes when eating something sour, such as a lemon . . .



So, think of the woman in the first picture, with the expression of the woman in the second picture, and you've got the image the author is attempting to portray.