Based upon your question, I believe you have a few misconceptions regarding Mary Shelley's Frankenstein. First, Frankenstein is Victor Frankenstein. Some readers, coming into the novel (even as they read the novel) believe that Frankenstein is the creature/monster. The creature/monster is never actually given a name. Second, Frankenstein never actually mentions angels. It is actually the creature/monster who mentions angels. That said, he only mentions one (Satan).
This conversation about Satan takes place in chapter fifteen. The creature is "narrating" this chapter (although in reality it is Robert Walton). The creature discusses his experience reading of Milton's Paradise Lost. The creature brings up the fact that he feels Satan "as the fitter emblem of [his] condition" (as opposed to Adam, who is not an angel). Outside of mentioning Satan, the fallen angel, no other angel is mentioned.