First of all, she is nowhere near the most Grammy nominations. Second, it is easy to get multiple nominations per year with song, record, album, video, etc. so numbers can get inflated pretty quickly.
While I vehemently disagree with her political beliefs, I must admit that Meryl Streep may be the best entertainer ever. She has 21 Oscar nominations (17 in a leading role) with three wins. Only one person ever won four in a career and she has nearly double the number of nominations as #2 on the list. It is almost impossible to get multiple nominations in a year for the Oscars so it takes a long period of consistency to rack up 20+.