C++ :: Error With Function With Objects As Parameters

I am creating code for a group project in my class. All my group members made a header file with an object in it with their functions. One of the functions in my partner's code uses a data member of mine in the function, so she has the function parameter a object of my object. (This isn't the code but for example)

class B {
friend class A;
void displayAthing(A object) {
cout<<object.thing<<endl;
}

I have this when I call the function in the cpp file

int main() {
A object;
B b;
b.displayAthing(object);
return 0;
}

However, when I compile, it gives me an error that the function does not take 1 arguments.