An allusion in literature is a reference to sources outside that book, including figures in history or characters in other literary works. An example of an allusion in Rebecca is in Mr. de Winter's conversation with Mrs. Van Hopper and the narrator. Mrs. Van Hopper asks him if his home, Manderley, has often hosted royalty, and he responds that they haven't since the days of Ethelred. Mr. de Winter claims that Ethelred was given the name "the Unready" when staying at Manderley since he was always late for dinner. This allusion enhances the idea of Manderley as historical, as Ethelred became king of England in 978.

Later in the novel, the second Mrs. de Winter is contemplating what to wear to a fancy dress ball that is going to take place at Manderley. Her husband, Maxim de Winter, tells her to wear a hair ribbon and to dress as Alice in Wonderland. This is another allusion. He is comparing the second Mrs. de Winter to Alice in Wonderland, who fell into a magical world. This comparison enhances the description of the second Mrs. de Winter's world as a kind of strange one filled with surprises.

I suggest looking at your question another way which may help to find an answer. It has been said that the novel, Rebecca, contains many allusions to the classic text of Jane Eyre by Charlotte Bronte. Both novels deal with an understanding (or misunderstanding) of passion in the motivations of the male protagonists, and both deal also with guilt in these characters too. Both of the female characters manage assert themselves as women. 

Each of the female characters is also presented as socially inferior to the men that they love, but each also manages to win the man she loves. As Jane tells us-

"Reader, I married him,"