Stiles has clearly forgotten that she’s already mentioned she recognises Scott from previous visits to the clinic. The expression Summer shows Scott is very much ‘yes I know he’s this kind of person and it’s okay I like him this way too’. Sympathetic. She would wave back, but both hands are occupied with unhappy cat.
“Hey Scott. I have an appointment, actually; it’s time for his checkup.” Helios makes the most pitiful mew possible, and hugs her neck even more tightly. She peels one set of claws from over her shoulder, and looks back up at Scott and Stiles, eyes merry. “Stiles, I promise we can do the friendship thing once we get this furball into a smaller room with no doors to the outside.”
At the very best, Stiles is not a person who could be accused of having a lot of presence of mind. He has indeed seemed to forget just about any conversation he may have had with Summer previously about knowing Scott. Instead, he just sort of buzzes around the edge of the conversation, in the way Stiles is wont to do.
“Let’s get him settled before he tears your shoulder to shreds,” Scott says to Summer, trying to give her a sympathetic smile. The little gesture he makes clearly means ‘follow me’, wherein he starts to lead to the open examination room. Stiles waits for Summer to pass through the wooden partition before he swings it closed again, stage-whispering seriously, “Mountain ash. Very important to keep it closed.” He thumbs the side of his nose briefly, and turns it into a guileless ‘who me?’ look when Scott turns to give Stiles a notable look over his shoulder.
Pressing one hand against the door to keep it open, Scott is gesturing to the room with his other hand. “Dr. Deaton should be here to check Helios over soon. Has there been any kind of—Stiles, don’t touch the sterile gloves, please—behavior or anything that’s concerned you, so I can be sure it doesn’t get missed?”
There’s Stiles in the corner of the room, retracting his fingers from the place where he was definitely reaching for the gloves to play with, flickering them as he does out of vague frustration that he’s been called out.
If she had a hand free, at this point Summer would have cuffed Stiles on the back of the head gently. She settles instead for lifting her eyebrows meaningfully at him, and making a mental note to ask him about the mountain ash. Why would it be important to have a /rowan/ barrier in a /vet’s/ clinic?
It does amuse her to watch the way Stiles changes under Scott’s influence — the little flashes of … responsibility seem to be absent, replaced with a higher level of clowning around. Summer untangles herself from Helios and deposits him on the examining table, where he leaves slightly sweaty pawprints and makes another pitiful meow. “No, he’s been behaving pretty normal, except for deciding to go out and /bring me back friends/,” she answers, making an exaggerated face of displeasure at Helios.
Then she winks at Stiles and Scott.