Had a similar experience in High School. Our Dean of Students retired mid-school-year and my chem teacher at the time took the job. He was replaced with a sort of permanent substitute for the rest of the year that was giving it an honest go, but couldn't connect with the students. Students started coming to me for help in the class. I seemed to be the only one that actually got along with the new teacher, so I pretty much acted as a proxy between him and the rest of the students; he would still teach the class, he would have me offer clarifications to what he was saying and do after school help sessions with the rest of the students.
Specific to your situation; I don't think you're going to get that teacher back with new teaching habbits. Not without somebody holding her hand and jumping on her during class (eg: assistant/student teacher). Your best bet is to try and get a sort of permanent substitute. When my Calculus teacher had to leave mid-semester during my senior year of high school due to her pregnancy, she was replaced a permanent sub for the rest of the year; a college student (math major). I'd tell your school to go for that. Try and find a college chemistry student that's looking to make a few extra bucks, and have them teach, and then offer after school help. In my experience, bouncing from sub to sub is not going to work. That's what happened in junior high school to my History teacher. She had to leave due to a pregnancy and was replaced with different subs every day. It's a clusterfuck because the subs to sync with each other. Sure, you have somebody in the room watching the students, but none of the information syncs in because the subs (try as they may) will never be in sync with each other. The only way the sub to sub routine will work is if there's only a week left of class. Then it's not that big of a deal, since the majority of the information on the finals will have come from the previous teacher anyway (and while she may have sucked, at least the source of information was consistent).
It's a touch situation, but in all the substitute situations I've gone through in my academic career, the permanent sub that actually knows what the hell they're talking about works best. Just make sure there's an offering of after school help.