In S4E1, we see Twilight Sparkle flying fast with Spike on her back. Heading directly towards the Golden Oak Library, she's going too fast to stop, so she teleports herself inside. Spike remains, keeping his momentum and crashing into the window (he was alright).
In S4E4, we see Twilight Sparkle with a ring, trying to keep it away from a bunch of bad
guysponies. She teleports away from them, taking the ring with her.
So my question is, when teleporting, what can she take with her, and what not?
Are there actual rules to that, or is it just as the plot demands / deems funny?