I'm in my mid 40's and stuff like this sticks out to me too. Especially slang usage. Such as the first scene when Rebecca and Jack were talking about having a family pool day and Rebecca says, "Right??" more than once. It is rooted in the phrase, "I know, right?" which I'm pretty sure wasn't a thing in the 90's. But I could be wrong...
Re Tess haircut and hat in the mirror scene. I took it as excitement. I thought it sounded like she gasped when she put the hat on as if she finally has the look she wants and is growing into herself? I could be way off..