So, how did Cheerilee and Twilight fall in love? Here's how it goes down in my AU:
Twilight doesn't create the "Freindship School". She does create one but it's called the "School of Harmony", which offers regular classes with mandatory extensive classes on harmony, ethics, sociology and so on. But what happens to the public Ponyville school? They merge the two and Cheerilee was assigned to plan out everything with Twilight. That's what brought them closer to each other and Twilight develops a dorky crush on her new work partner. Cheerilee starts reciprocating the feeling at some point and I think you know what happens next: asking out, awkward first dates, dorky gifts and all of it lead to a strong marriage of Princess Twilight Sparkle and Miss Cheerilee