"When you began talking I recognized your voices, then I heard my name mentioned, and true to the old adage about listeners I heard no good of myself.
When I heard Miss Briggs's name spoken I decided that under the circumstances I was justified in listening further, as I intended at any rate to announce my presence and just what I heard as soon as you two had finished speaking.

Miss Wicks's sudden departure prevented me from carrying out my intention as far as she was concerned.

I shall, however, notify her at the earliest opportunity." Grace paused, looking squarely at the older girl.
Beatrice Alden's expression of intense displeasure gave way to one of reluctant admiration with dislike struggling in the background.

"You are extremely frank in your statements, Miss Harlowe," she said sarcastically.
"There is no reason why I should not be," returned Grace composedly.
"Miss Wicks and Miss Hampton, for reasons best known to themselves, chose to make Miss Briggs the victim of an unwomanly practical joke on the very day of her arrival at Overton.

I think you are in possession of the story.