Hi Alex,
I don't fully understand what you mean in sentence 1 and 2.
The third one should be ''她病得很严重'' (严重 = grave)
Other similar examples :
她病得很严重 = She is critically ill. (病 = ill)
她玩得很开心 = She plays happily. (玩 = play)
她哭得很难过 = She cries sadly. (哭 = cry)