Complex sentence: Rachel kisses a sober Blaine, which makes him realize he is indeed gay, but instead of being disappointed by this, she is elated: she tells Kurt that having had a relationship with a man who turned out to be gay is "songwriting gold".
Split into simpler sentences: Rachel kisses a sober Blaine, which makes him realize he is indeed gay. Instead of being disappointed by this, she is elated, and tells Kurt that she is inspired by having had a relationship with a man who turned out to be gay--she calls it "songwriting gold".