I actually don't think Willow was being selfish. I think she really did think Buffy was in a hell dimension.
I can see were your coming from. But the thing that has bugged me about Willow's line of thought is that Buffy's body wasn't sucked into any dimension. Willow knew about Angel. Buffy went through what happened with him in season 3. His whole body was taken to the other dimension. Now, I know there are other dimensions, but I would personally be thinking that Buffy's body hadn't been sent any where, so the chances are she wasn't anywhere other than where she deserved to be. If that makes sence 🙂