In re: Tai's participation in the mother-daughter bong bonding and whether Tai is stepping outside of the boundaries set by her position, allow me:
I was, for 25 years, part of a newspaper newsroom staffed largely by young people not too long out of college, living far from wherever home had been, and in a community that drew definite lines between who was "from here" and who wasn't. Naturally, the young co-workers became social. The younger echelon of the newsroom became a family (sometimes literally; I can immediately think of three -- no, four -- marriages whose spark was first struck on deadline). I know that some of my most enduring friendships were formed in my first two years there, while most of the co-workers who came after (particularly as I became "too old for this sh!t") blur together in, or drop out of, my memory.
These relationships brought the minefields one might expect, the hurt feelings and the favoritism, and I won't argue with anyone who wants to doubt the appropriateness of this, but that doesn't change the reality of them.
My point is that the judgment of whether Tai crossed a boundary may be muddied by the fact that, in such a workplace/social situation, the boundaries may be blurry indeed.