The AI on her A3 is very unreliable and ineffective in two ways:

1.  Seems to always target leader regardless of who needs healing (even if leader is at 100% hp).

2.  On default priorities often chooses A1 over A3 even if healing is needed.

My guess is that under the hood, the game doesn't consider it a heal, thus it just defaults to casting on the leader no matter what, if so just change the AI to consider it a healing spell.