What she needs is a personal downfall beyond sheer stubbornness. Something that she truly has a hard time overcoming in herself.
Which admitting her Bruce Wayne syndrome would cover! The fact that Applejack's parents died, and since Granny Smith's not in field-work condition, it's up to her and Big Mac to take care of the farm.... by themselves.
Having the weight of losing her parents as a filly, and helping raise Applebloom AND help out with the farm, taking up the weight of their home left behind from the parents is a BIIIIG thing.
And, whereas she doesn't show it, I'm sure her situation bears down on her in her personal time. Something that probably makes her cry to herself every now n' then.
Also, what if the hats and ribbons kept in the closet fer those things, were actually left behind by their parents? (Headcanon names are Timberjack and AppleBlossom)
We really need a family episode. Perhaps Applejack and Scoots can click in this department due to their lack of parents(orphan scoots is backstage canon btw)? Perhaps we hear about Rainbow Dash only being raised by her Dad?
Where's Fluttershy's parents?