"She is going to find her husband."
Translation:Ella va a encontrar a su esposo.
That sentence would mean "She is going to find her husband for him/her/you" The "le" is not needed because the husband in this sentence is a direct object. "Le" is only used for indirect objects. Two acceptable answers would be "Ella va a encontrar a su esposo" or the more ambiguous "Ella lo va a encontrar."
I think it's more because they consider "going to find" a synonym for "to search" in English, but I don't know because they don't ever explain any mistakes you make on Duolingo. This not explaining and the ambiguity in translations is really a downside to Duolingo which by the way I think is a really very great website. They should really look into it though!