How does the author use situational irony in the novel, The Naked Mole-Rat Letters?

One example of situational irony can be seen in the way Frankie makes up ridiculous lies in an effort to dissuade Ayanna's interest. Although Ayanna has undoubtedly realized most (or all) of these stories are lies, she has not called Frankie on them. Ironically, Frankie's fellow students have discovered that Frankie has spent time with a boy named Johnny Nye, and they have started making up stories about that relationship. Frankie's personal situation comes to a crisis when another student writes a love note and signs Johnny's name to it. Frankie is horrified by the situation, though she has done the same thing by sending Ayanna emails and signing her father's name.