Fraysong's outburst is unexpected from Terezi's point of view...but not entirely unreasonable. Here he is, trying to introduce his friends, and they're making it more difficult on him than it really needs to be.

She frowns at him when he makes his plea to her. Did she have to be making a whole thing of this?... No, not really. It's not like she knows enough about the other man to make a case for proper Foresight usage. Her comment was only based on the little bit he had said... Honestly, she didn't know what this stranger was like at all.

But when he concedes to her point, the tension leeches out of her. "It doesn't have to be a thing," she concedes in return to the Initiate. Then to Sigma, she continues: "...I'm pretty sure that Foresight never stops being a learning process. I didn't know that I couldn't See what would happen when other Seers--espers, whatever--acted on their visions. I've never actually met another Seer like me before." Not exactly, anyway. Rose was a Seer, but her powers were a lot different. She's not even sure they See in the same manner, or the same kinds of things. She never really bothered to ask, either.

"I'm sorry for attacking you," she adds, trying for casual and hitting somewhere between that and awkward. "I didn't know what else might happen, and I panicked."