Shamefully has two close uses, and both grow out of shameful. First, it means “in a shameful way”: someone behaved shamefully at dinner — the manner itself deserves blame. Second, and this is the one students often miss, it means “to a shameful degree”: the animals were shamefully neglected; the room was shamefully small for so many people. Here it is not that the neglecting “looks ashamed.” It is that the neglect is so bad it ought to make us ashamed. The word is a little formal, at home in news and complaints. In speech, people may just say really badly or it's a disgrace.