Well, when you like about it Nightmare Moon WAS Luna's flaw, and the reason she acts perfect is probably to make up for her mistake of causing Celestia problems as Nightmare Moon. With that said, she does have a few other flaws, she's socially awkward, she's clearly a doormat/pushover, and she does get envious of Celestia.
Sorry for jumping on the defense, but I really love Luna, a lot.
Well that's true, and I guess I like a lot more because she's the ONLY pony I can relate to. And yeah if you had no friends you'd want some help to get a few, after being trapped in anger and envy for so long, being alone for 1000 years, being remembered as a monster. It's just a little difficult to make friends after that.
I know it Luna and not Fluttershy, Luna is a little bit of one though, how she always goes along with Twilight's plans in the nightmare night episode, even when she says no to it, Twilight tells her to come on and she does.
I don't like how the fandom sees her either, she's a socially awkward princess not a helpless baby, jeez people.