Bellatrix was intuitive enough to know that something was going on, Skeeter had never so much as looked twice at her before. This strangely personal line of inquiry was ringing alarm bells -- loudly -- right in the very centre of her brain, but she wasn't sure what it was all in aid of yet. She still presumed it must be about Rodolphus, Blishwick didn't so much as enter her thoughts. This was a common theme with Bellatrix -- she picked people up and then discarded them like toys; Blishwick served a purpose, little more. That the girl was besotted with her was hardly her concern.
Bellatrix did not fluster easily -- she wasn't embarrassed, only irritated by the intrusion. She was used to having just what she wanted and when she wanted it -- generally speaking people were not supposed to pass comment.