As if "fall in love" couldn't already tip him off.What could she say that wouldn't tip him off that she's dumping him?
Again, she stops mentioning the childhood friend completely after 26. Doesn't sound like a huge barrier you are talking about.
She hears about him saying that he's been in love with someone for a long time, so yes, combining 2 and 2 she comes to that conclusion, especially with all her efforts to make him forget about her.Chapter 13.5 makes clear that she thinks the CF is the best candidate b/c she thinks he's already in love w/ her.