Your gender counterpart gets retconed to be only a proffesor's assistant and Shauna's actions changes depending on the gender you play.

>If you choose male player
She gets a crush on you and to be close to you she decides to be your rival, besides having more interest in hoenn contests than battles.

Once you beat her in battles she rewards you with heart scales and/or sweet hearts.

>If you choose female player
The assistant gets in contact with you often only as a meessenger/deliverer of lab stuff.
But Shauna gets jealous of you thinking you both have something, so she decides be your rival to show whos best to get his attention

Once you beat her in battles when you find Calem in the scripted encounters, he gives you the heart scales and/or sweet hearts that Shauna gave him because he doesnt need it but those are more useful for trainers like you.

>Resolution
Her story arc ends when she notices that you or Calem doesnt have interest on her, blaming her self for reading too many romcoms.

Then decides to go back to Aquacorde to start amateur and unnoficial pokemon contest in hoenn style, you can participate too. You can rematch her once a day. Before you challenge her she talks to a bored Trevor about her new crush on Dexio.

Her final team is:
Advantageous starter
Sylveon
Goodra
Snorlax
Azumarril
Altaria