Rather than duplicate that information I will provide some sources and a bit of new information I found on Maggie during my research.
A newspaper report of 1875 indicates Maggie was touring with the Fisk Jubilee Singers.
The 1880 census for Davidson Tennessee finds Maggie with her 74 year old mother Ellen Porter born North Carolina and older sister Sarah. In this census Maggie's occupation is given as "Jubilee Singer" and sister Sarah's is "works at Jubilee Hall"Collection: African American NewspapersDate: April 15, 1875
Publication: THE CHRISTIAN RECORDER
Title: THE JUBILEE SINGERS
Location: Philadelphia, Pennsylvania
THE JUBILEE SINGERS.Philadelphia has once again been enraptured with the strains of these famous singers; and never before did they appear in better trim, and consequently to better advantage. At the farewell Matinee of March 10th, they really seemed to outdo themselves. Although we have often heard them; yet never did they sing so sweetly. F.J. Loudin in such songs as Rock me in the Cradle of the Deep , and his celebrated Laughing Solo, proved himself to be a very prince of song. So pleased, especially, was our eminent citizen, George T. Stuart, who occupied a seat on the Platform, with one of Mr. Loudin's performances that unpinning a beautiful rosebud from his own caller, he proceeded amidst the plaudits of the vast company to adorn the successful basso. Having hazarded the individual mention of Mr. Loudin we cannot possibly fail to recur to the singing of Hope Beyond by Misses Jennie Jackson and Maggie Porter. It was absolutely bewitching, as the audience enthusiastically testified. Indeed it may be said, that, without an exception they all are superb singers. That their audiences are of the same opinion, is evidenced by the almost unreasonable demand made for repetitions. One thing is noticeable to him who keeps his eyes open, - the students themselves are fast outgrowing these songs of their grief-stricken parents, and in singing not a few of them they themselves seem to enter into the spirit of the audience, and are constrained to smile at the weirdness of their own music. While this detracts somewhat from the entertainment, it is certainly no more than what ought to be expected. Freedom has its fruits as well as slavery. Let the Jubilees return to Philadelphia, when they will, and if we are to judge of the past, a glad welcome will be sure to greet them.
Source: Accessible Archives
As Maggie L Porter Cole she applied for a passport in 1897 and gave her date of birth as 24 February 1855 in Lebanon Tennessee. Her occupation was a concert singer.
She also applied for a passport to England in 1895.
I next found her as a 43 year old in the 1900 census for Detroit Michigan with her husband Daniel Cole 46 and children Imogene 17, Daniel 16 & Singleton 14.
Maggie says her father was born in Kentucky and her mother in North Carolina. She is also found with husband Daniel in Detroit in 1910.
The 1930 Detroit Census records her as a widow living as a boarder.