Good eye. My own suspicion is that it’s just a unicorn - the six pointed star could be a simple reference to unicorn magic, and it displays a forest. Considering unicorns lived in a forest at the time, it makes sense… Still, it could be a reference to Twilight herself. Even if the six-pointed star was the symbol of magic in ‘old equestria’ (which itself is more of a theory than anything), there’s no reason that Sunny’s father would know that…