Did she not go in their ways?
Rashi #1: If only you went in their ways, and were not more abominable than them! Also "v'Lo Yutan Na l'Avdecha" (Melachim II, 5:17) and "v'Lo Im Odenu Chai" (Shmuel I, 20:14) of Yehonason.
Rashi #2: You did not want to go in their ways, for their abomination were small in your eyes, so you corrupted more than them.
Radak: You were worse than them.
Malbim: The ways are ways of the Nefesh; actions sprout from them. You did not go in their ways ? the ways of the Nefesh of Bnei Yehudah were different than Sedom and Shevet Efrayim. Bnei Yehudah believed in Hashem, and the Mikdash and Avodas Hashem were constantly among them. Efrayim and Sedom denied Hashem and cast off primary principles of Emunah. Even so, you did like their abominations. Also you served idolatry, even though your intent was that it be like charms to draw influence from above. You believed in Hashem and His ability and Avodas ha'Mikdash Hashem fter
Why does it say "Kim'at Kat va'Tashchisi Mehen [b'Chol Derachayich]"?
Rashi #1: Had you not been worse than them, your abominations would be small in front of Me. However, you corrupted more than them (Targum Yonasan).
Rashi #2: Refer to 16:47:1:2.
Radak: You stood a short time, i.e. 23 years, after the Galus of Shomron, and corrupted more than Shomron and Sedom. Galus Shomron was in Chizkiyah's sixth year; 23 years of his reign remained. After him, his son Menasheh was worse than all before him. Kat is like Me'at; the matter is repeated in different words.
Malbim: Shortly after, you made your ways worse than them. You joined Shem Shamayim to another matter (idolatry). You served Hashem in His Mikdash, and joined to Him Pesel ha'Semel to be a colleague to Him and help conduct [the world]. This is a corrupt Emunah, worse than the way of Sedom and Shomron, who said that Hashem abandoned the land, and totally denied Him. They did not make a rival for Him, to join with other gods.