The lady in a lab coat - probably about Senku's age - who entered doesn't look very impressed. What she does look like is an older Haibara, including the penchant for lab coats.

Information on Voidtreckers was sparse, but Shiho had two things to look out for: armbands, and people wearing primarily red, blue, purple, or.... orange.

Her eyes were, therefore, on Senku's armband like a hawk.

"That seems rather... doubtful," she replies finally.