Personally, I think you're making a big fuss over nothing (just like someone who said something was fishy with Tataru because she said she felt a little tingle when attuning to an aetheryte).

Tataru was just smiling, and in hindsight her comment was pretty obvious foreshadowing of what was going to happen. It's just a literary device, nothing sinister or foreboding.

In regards to not catching on to the shell game Teledji was running, she has thus far shown herself to be innocent - and the problem with innocent people is that they tend not to be very suspicious of others and take everything at face value. She is the Scions' secretary, but she's also been working as a miner collecting crystal clusters (etc.) to help with the upkeep of the organization, and also had to spend time learning to sew and work leather at some point during 2.x (since the first real thing she does upon arriving is make Alphinaud new clothes).

How she got the funds for Y'shtola's new outfit? Well, chances are the Scions' back account was private, or as secretary she kept it all on herself (seeing as I'm carrying around ~5m gil right now, don't bring up quantity of currency). With the Scions more or less disbanded during 2.5.5's ending, she alone would have access to all those funds, so...