my guess is, since it's a name, they went with how it is said, with a little less accent... so sui do-rii-mu became sui dream....
it's kinda like how in eureka 7, eureka's name is not pronounced 'yoo-ree-ka' like the word is pronounced in english... they kept it the same as the japanese but with a little less accent... so 'e-ool-lre-ka'... became 'el-re-ka...'
tokyopop's translation of the rozen maiden manga takes way too much creative licence... changing desu to 'yes' was a bad move (it should have been left as desu, or cut out all together, none of this half measures crap)... and they miss spell suigintou at least once (suginto or something) so i wouldn't exactly trust them... besides, geneon wouldn't talk to tokyopop about their dub, they would listen to their own translators.
my dodgy hong kong DVD's translated everyones names in the subtitles... so shinku became 'ruby'... suisei seki became 'jade'... sousuiseki became 'lapus lazuli' etc... i think they translated suidream as "jade dream"... (tomoe became 'bar'... of all things... so it could have been worse...)
still... at first, i thought suiseiseki said 'come out 'silly-dream'..." when she first summons her artificial spirit...
EDIT: i dunno about consulting peach pit (since they're the manga artists, they probably didn't have very much to do with the actual anime production) but they would have gotten the original script with the visual/audio masters from TBS (the guys who made the anime)... and they would have consulted with the original director about this or that... i think when anime is licenced, a lot of time, it's part of the contract that all 'creative changes' have to be run through the original japanese director to make sure he's fine with it... otherwise... we would end up with a dub like the 'one piece edit'...