Definition of "YGTBKM"

“He fired back at her, blaming her for their breakup, saying she was self-absorbed and always put her own needs above his. He predicted that by the time their senior prom rolled around, she would regret letting him go. To which Claire responded: YGTBKM. SWL.” ¶ “Translation?” ¶ “'You've got to be kidding me. Screaming with laughter.'”

2008, Maureen Smith, No One But You, New York, NY: Dafina Books, page 109