Most of the components of your story are sound. Only a few issues I thought worth bringing up.
In chapter one, Shelly gives her father a head start in a police carriage and still somehow gets in front of him to a destination he didn't tell her about to tackle two thieves at the same time. Also, I find it difficult to believe two thugs would surrender so quickly if they were up against a 12 year old filly who managed to tackle them. Of course, it might be because they got tackled and knew they couldn't outrun the police coming after them any more as the reason they surrendered. Just something to think about.
In chapter 2, the only thing I'm raising a flag on is Cal Gold's interaction with Shelly. It's a hard pill for me to swallow, due to how many coincidences happen at around the same time. A new recruit on his second day lost on campus, probably not the top of his class. He bumps into Shelly by accident, because neither of them were paying attention. Either he's trying to start a conversation, or he forgot where the colt's dormitory was from yesterday, unless he slept outside or something that night. Regardless, her friend Ella Raindrop is a professional shipper and ships her with every stallion whom has a 15+ second conversation with her that she sees. And when she ships, she ships hard; hard enough that Shelly actually start giving it thought.
This is fate conspiring to force the pairing to work. I'm fine with them bumping into each other for no reason and talking for no reason, but I don't agree with any lasting impression to occur within this scene. We already know that this meeting is somehow relevant because you bothered showing the event, but not every other time Shelly bumped into ponies and had to give them directions. Cal is going to be a significant character and it's good to know the first time the two met. Ella just kinda ruined it for me there with her relentless pursuit of the subject, though. I would suggest waiting until after a second, more significant meeting between the two later on, that Ella actually has a chance of seeing, before she teases her friend about it.