I think I'm right, I just found the following passenger list that indicates Fredericka Fehrmann, my ancestor, traveled to WI with Friedrich, Carl and Caroline.
Ten Old Lutheran Passenger Lists for Lutherans that went to Buffalo Erie & Niagara Counties, NY and Dodge, Jefferson, Washington, Oazaukee, and Milwaukee Counties, Wisconsin in 1843. by Martin Wm. Johnson. (the numbers after the name are the page number - I'm trying to find out how to get a copy of the document.)
Fehrmann, Carl 6 Fehrmann, Caroline 6 Fehrmann, Friedrich 6 Fehrmann, Friedrika 6