I just found Lillie Constable, age 17, in the 1880 U.S. census in St Louis living next door to the Reuben Caffall family. I also found another 1880 U.S. census records listing her name as Lottie, living next door to the same family in St Louis. The difference is the enumeration district number, I posted a question on ancestry to ask about the difference in the two records. Nonetheless, here we find Lillie (Margaret May Caffall's biological mother) living next door to Reuben, Nellie, and 7-year old Gertrude. This is the year her father Nathaniel passed away and I'm sure the Constable family is in turmoil. I'll have to look at this family she is with, curious as to why she is a boarder with this family versus the Caffall family next door. Thanks again for you help on this particular puzzle, I appreciate it.
*Edited - just realized that the census record with enumeration district 112 listing her name as Lottie was stamped rejected.*