Can literary texts, such as Rebecca by Daphne Du Maurier, be defined as 'popular' in one context be defined as 'elite' in another?
This is a great question. It is probably best to start with this maxim: context is everything. So, to answer your question, it is possible that a text is popular in one context and elitist in another context. It all depend on the people who are in that context. Let me give you a few examples.
If you are reading Homer's Iliad in college and you are discussing how he uses formulae in a seminar, then the quoting of obscure lines of Homer is not seen to be elitist. This is what you have been doing for weeks. In light of this, we can say that the quoting of Homer is common or popular. However, if you quote Homer and his use of formulae at a dinner party where no one knows who Homer is, then you would be considered a elitist.
Similarly, we can say that same with a novel like Rebecca. It all depends on who you are with. The novel, Rebecca by Daphne du Maurier is not something that all people know. So, for example, if you quote the opening lines of the book, which are probably the most famous, "Last night I dreamt I went to Manderly again," and you expect the average person to know it, you can be seen as an elitist.
This question I think, greatly depends upon the canonization of the novel. It has often been the case that popular novels as Jane Eyre was during the time of publishing, as well as novels from Dickens have been canonized as literary classics with time.
The canonization of Rebecca may just require time to become a literary classic. It also depends upon what criteria make a work enter the canon. This could change.