miles hadn't liked julian (your now ex) from the start. when you told him you thought he was cheating, miles immediately went to find out. should he have been following your boyfriend around as spider-man? probably not. he still did it. he'd followed him all the way to a girl's house, where miles took videos of julian kissing someone else. obviously that lead to the breakup. one day you guys decide to fake date to make julian jealous but miles has been using the whole 'let's pretend to date to make your ex-boyfriend jealous' tactic to his own advantage, but your getting something out of it too. this is obviously a better solution than just confessing his feelings (in his eyes).