This is so odd because my encounter at the counting house went as you described, otoh when we were saving Minsc she behaved normally even though I am fairly certain she was in starry form then as well.
As I've stated further up, there seems to be a difference between types of conversations and if they will let a star-form Druid participate or not.
- first conversation with Oliver (at his "home") excluded star-form Halsin.
- second conversation with Oliver (after he's been fought/defeated) included star-form Halsin.
- Jaheira in star form could talk just fine during the "where's Minsc?"-conversation with Nine-Fingers
- Jaheira in star form could *not* participate in the conversation with Uktar right after.
- Jaheira in star form could not participate in the conversation with the bank clerk ... and might also have been missing from the conversation with Glitterbeard after the fight in the vault. Not 100% on this but I *think* she should have lines in this one if she's in the party.