I always got this sense she was a young pony trying to act like an older pony. But thanks to Twilights help and understanding, she's gone back to acting her real age, a pony just coming oUT of her teens . (19-20)
And it fits. Her village was only about a couple months old when the Mane 6 arrived. Timeline for me:
18----- Starlight leaves homes and goes about setting up her village.
19---Driven from her village by Mane 6
20-- Time Travel, redemption, than becoming Twilight's pupil
Meaning she was still technically a child/teen living at home when the first 3 seasons were happening. Left home around the start of season 4. Started building her village around the midpoint of season 4. ( Maud Pie flashback did show the village still in the process of being built sometime after season 4 episode 18)
Actually, she might actually be close to Spike's age, if slightly older, which might be why she gets along with him so well and kind of treats him with a little more respect than the Mane 6 .