Attack of Opportunity has this trigger:
A creature within your reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it’s using.
If you are riding, none of this applies:
- uses a manipulate action: Command an Animal does not have the manipulate trait
- uses a move action: Command an Animal does not have the move trait
- leaves a square during a move action it’s using: the rider leaves a square, but it is during a move action someone else (the mount) is using
- it is obviously not a ranged attack
Am I correct you cannot make an AoO against the rider, only the mount?