What is the timeline for the first Season of Maria Watches Over Us?
The episode numbers relate to the order they were broadcast. chronologically speaking in the series Episodes 7, 8 and 9 occur after Episodes 10 and 11 with Episode 12 occurring after 9. 

According to the linear notes in the bonus menu of the RightStuf DVD (Disk 3), the Valentines Day Episodes were aired earlier as the initial broadcast date for Episode 7 fell on/around February 14 which is Valentines Day. 

Because the 3 Valentines Day Episodes are tightly connected together in terms of plot they couldn't just broadcast episode 7 and be done with it so the 3 episodes was broadcast in sequence and 10 and 11 broadcast after before the conclusion of the first season.