[@Prince of Seraphs] The constellation thing was for Adelon, not this rp.  ^.^;;  Just something else I did that got incorporated somewhere, to my immense pleasure.

For Sini's lack of significant dislike, I'm going off of her preference for prioritizing long-term benefit and her considering nature.  Yes, she might have a knee-jerk reaction to Tuatha de Danann.  If she suspects they are planning something, it is for the reasons you stated.  But a little tolerance can go a long way to avoiding future trouble, and if you treat someone who is often an outcast with simple courtesy they are likely to regard you well.  And as you yourself have mentioned, Raven wasn't around when her kind let the fey down.  Not to mention that, historically, there was a war and the Tuatha de Danaan did win, if at a price.  They were arrogant and foolish, but Sini herself has fallen into that trap.  Especially with the Fir Bolg teaching humans how to fight fey, I believe she judges the scorned retreat the wise decision, even though it was an unpopular one.

So yeah, instinctive bias but tempered by deliberate consideration.