After Sita was exiled by Rama,why didn't she go back to Mithila?
Isn't she Mithila's princess?Even if she didn't go, why couldn't Janaka arrange for his daughter Janaki's protection in the jungle?
The episode of abandoning of Sita by Sri Rama appears in Uttara Kanda of Valmiki Ramayana.
UTTARA KANDA is a PRAKSHIPTA/an interpolated story - an insertion made at a later date. Ramayana ends with the coronation of Sri Rama as the King of Ayodhya.
A 6th Century version of Ramayana was found in a library of Kolkata. According to this version, there are just five kandas (sections) instead of the accepted seven. There is no Bala kanda or Uttara kanda.
As the episode of banishment of Sita finds place in this interpolated Uttara Kanda, further queries like whether Sri Rama was justified in banishing Sita or Why did not Sita go back to Mithila, etc, may not arise.