Bart had hurt Lily in a different way. I don't think she would forgive Rufus if he was the one that hireed someone to look into her past. I mean... It's AWFUl! O_o
And Lily loves him. She knew she has made a mistake and she wanted make it up to him. She hurt him...
But she understood and tried EVERYTHING to make him forgive her.
Those are not WONDERFUL arts. LOL Me and my friends were bored LOL