It's true about BECMI, but she is going to represent chaotic metallic dragons now, too, so I think we need to go with CN.
Well you seem more committed to this question than I am, so I'll accede to your preference and make her Chaotic Neutral.
I was thinking The Great Dragon would likely be pure Neutral, so I guess Diamond will be Lawful Neutral when we get round to him.
Come to think of it, I'll go through and make sure all Pearl's gender pronouns are correct in the text. There are a few stray "him" and "it" that should be "her" and the like.
It's true about BECMI, but she is going to represent chaotic metallic dragons now, too, so I think we need to go with CN.
4th: chaos hammer (D), control water, cure critical wounds, dismissal, freedom of movement, inflict critical wounds, restoration, tongues ??
She's already got
chaos hammer as an at-will SLA so we need to swap that out.
Also, shouldn't she have telepathy and/or
tongues as a Special Ability. Isn't that a standard feature for divine-equivalent creatures in 3E?
…well that's curious, I checked my notes and for the current 3E Dragon Rulers:
Bahamut the Platinum Dragon had telepathy and
tongues in 2E, but neither ability in 3E.
Tiamat the Chromatic Dragon has
tongues in 2E, but neither telepathy or
tongues in 3E.
Gruaghlothor the Ferrous Dragon has "an ability to communicate with any intelligent creature" in 2E which Enworld converted to a telepathy 120 ft. SQ in 3E.
Sardior The Ruby Dragon has telepathy as a SQ in 2E. In 3E he has "read all languages and speak directly to all beings within 8 miles" and presumably can use his knowledge of all psionic powers to speak mind-to-mind if necessary.
How about giving Pearl telepathy to, say, a few hundred feet? Maybe 300 feet like the majority of 3.5 edition Demon Princes (i.e.
Demononicon entries)? I'd go down to 200 or 150 ft. if that seems too high, but wouldn't fancy 100 ft. like most 3.0 Demon Princes had (i.e.
Book of Vile Darkness).
I've just noticed Sardior's WotC website stats don't list a manifester level for his psionics. If he uses the default SLA caster level for divine rank 8 he'd be CL 18th, which is lower than all his thanes who have CL 21 or 23 (or rather ML). Plain old
mindlink is only Telepathy 1 and with ML 18th has a 90-foot range for establishing the link, which is "works over any distance (although not from one plane to another)" once established. I'd think he'd be, say CL 25+ to be higher than his minions though, which'd give his
mindlink a 105+ foot range.