Creerse
 

Se cree la heroína de las novelas que lee.
I suppose it means she sees herself as one of the heroines of the novels she reads.

I would not have written it this way, I would have written,m I Se cree que es una de las heroinas de las novela que lee.


Am I wrong? Are both sentences correct?

Both sentences are grammatically correct, but adding 'una de las heroínas' changes the meaning. She believes that she is the heroine of the novels she reads.

With the correction made by Rusty, both sentences are OK, because there is the verb creérsela, which includes lexicalized pronouns, with that meaning of having fantasies, or delusional thoughts, or merely half cooked convictions of being something or having some qualities or merits that aren't there.

Le dijeron que cantaba muy bien [como elogio amable o simple cortesía] y se la creyó. Ahora está buscando empezar una carrera en la industria de la música. [and whoever told that is not the flattering culprit but the people who build themselves a castle using just one pebble]