Rashi says: אֶפ רָת ים means Chashuvim (aristocracy), and the Seforno says that although they were Chashuvim, they still didn't get involved in helping the Tzibbur. The Alter of Novardok Zatzal said that the main Achrayus to do Zikkui HaRabbim for Klal Yisroel is on the Bnei Torah. Who were seen riding in a car on Shabbos during the Holocaust to save Yidden? The two Roshei Yeshiva of the biggest Yeshivos: R' Avrohom Kalmanovich Zatzal and R' Ahron Kotler Zatzal (Mir and Lakewood).
When Avraham Avinu pleaded with Hashem to save Sedom in the Zechus of the Tzaddikim, he said that maybe there are some Tzaddikim: ב תוֹךְ הָע יר “in” the city. RSRH Zatzal explains that: הָע ירבְׂתוֹךְ “in” the city means Tzaddikim who are involved in helping the city, i.e., a Tzaddik who doesn’t live only for himself but is concerned about his surroundings. Chazal say that: אֶפ רָת was Miriam. It is indeed a fitting name for her, since as a small child she was Chashuv enough to tell her father, Amram (the Gadol HaDor) that decree of divorcing Yocheved is worse than Paroh’s decree, since now Klal Yisroel won't even have girls.
It's nice to be a Chashuva person, but being Chashuv means having Achrayus for the Klal, at least in Tefila, like the Gemara in Makkos which blames the Cohen Gadol for people who kill: ב שׁוֹגֵ ג by mistake, since he didn't daven enough for his Dor. Miriam was indeed Chashuv, since from birth all she cared about was Klal Yisroel. She is the epitome of a Chashuva person, and: אֶפ רָת fits her perfectly.
