Sentence:  It made him pretty hot under the collar , after the idea Miss Sis had given him , to be told by Miss Kiz that her holy spa was all reserved for this summer and next , if you please , and that much as she <WSD>regretted</WSD> it , they would be unable to entertain Mrs. Robards and the children . 
Meaning of the word marked with <WSD> tags:  feel remorse for; feel sorry for; be contrite about