Let's talk about why I'm obsessed with this brief, dialogue-less scene.
One quote of Kristin's comes to mind: "We rarely see her rattled... I realized that with Pam, she's been so together for so long that the slightest bit of rattle looks really big."
Each gif illustrates a shift in very extreme emotions that I will go through individually because Kristin is a master of nuance here, and with Pam in general.
#1: Joy. You can see very subtly that Pam is elated and relieved to see Tara alive and okay at camp. However, she can't reveal too much because as she has brutally experienced before with Eric, and Eric with Nora, letting anyone here know who your family is/who means something to you is extremely dangerous and can be cruelly exploited. Plus, being Pam, she rarely shows much emotion anyway, even with Tara, but it's undeniable that her eyes light up upon seeing her.
#2: Concern. Pam overhears the announcement about Tru Blood and her smile quickly fades. Still, she is trying to mask her worries because she can't let on that she knows about what's going on with the Hep V. Nevertheless, her eyes shift to the man speaking and serving the blood and you can see the fear start to grow in her eyes.
#3: Panic. Tara is now in the line to get the drink, within seconds of possibly ingesting it, and Pam doesn't know if she is informed about the danger here. Her eyes shift back to her progeny, silently trying to convey a warning as well as hope for a sign that Tara knows what's going on.
#4: Relief. Tara can read Pam like a book and can see the fear in her eyes. She reassures her with a "I know" and Pam nods, again holding in her emotions and not letting on the flood of relief within her in order to remain cautious and unsuspicious. As soon as she is comforted that Tara is safe, she scans the room and puts up her stern default expression.