HG is a very very bad version of morning sickness. Really, superbad. Mothers can become ill very quickly if they don't consume any liquids for a few days, and they really do need to seek help. And maybe now that Her Royal Highness has kindly shed some green-tinged light on a serious condition that affects 1% of expectant mothers.
This girl could have had a husband, a tiara, a baby, a title, a palace, and her own specialised bottom minder by now. She could have been defined by her slimness, her reproductive abilities, and how long she could spend waving to commoners before her arm got tired. Instead, she's free to do whatever the hell she wants with her life.