I don't think that Donna has any hidden feelings, but as far as the Doctor goes, he totally loves Donna! You can totally tell sa pamamagitan ng the way he reacts at the end of Journey's End and when he sees her on the kalye in End of Time Part 1. Whether or not they are in pag-ibig 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.