Unreported Sub

[NSABlue]

Depends on which set of rules you're using. In NFHS, as long as the unreported sub had entry/re-entry rights in this slot of the batting order, the play is legal. You would issue a team warning to the offending team and play on. The next violation by that team would result in the player being restricted to the bench.
In NSA Fastpitch, an unreported sub is treated like an illegal player and is handled like a protest. In your scenario, the unreported sub would be declared out. Both the sub and her coach are ejected and any advances made by other runners as the result of play by the illegal player are nullified. Not sure about ASA but there are lots of ASA umps that can help.