I don't think that Donna has any hidden feelings, but as far as the Doctor goes, he totally loves Donna! Du can totally tell Von the way he reacts at the end of Journey's End and when he sees her on the straße in End of Time Part 1. Whether oder not they are in Liebe doesn't matter, they just belong together!
I think Donna and The Doctor loved each other as close friends. They had such a strong bond and despite thier bickering they still worked together as a team. They had fun together and the Doctor felt comfortable telling Donna personal things.They basically had a really strong and loving friendship.