She is one of the missing souls to be located in the "Missing Persons"side-missions. She is found at Armadillo (in the bank, to be exact) and needs to be returned to Fort Mercer. She is also a defender of Armadillo, and she, or someone with a strong resemblance to her in voice and appearance, can strangely still be found defending the town even after her rescue (and even during it, creating a situation where one can encounter two Adriennes). She is usually on the upper floor of the barn.
After Armadillo is saved and if Adrienne survives, she can be found on the balcony of the saloon talking to and smoking with Jessie Hargrove.