I have three children. My middle child, Caleb, is currently 13. He was diagnosed w type 1 when he was three. I'm sorry that your daughter was diagnosed. It's completely understandable that you are overwhelmed. I know I was and to be honest, I didn't realize the extent to which I was overwhelmed until years later when I could more objectively reflect upon those early days, weeks and months.
Every person and family living with diabetes has choices to make which will impact how you treat it. In general, the advice we were given and mostly abide by is to lead a normal life, and work diabetes into it. That includes diet. Since Caleb was diagnosed, I've become more knowledgable about nutrition. I always tried to make healthy choices for my family, and even moreso after Caleb's diagnosis. But diabetes doesn't dictate what we eat. Caleb eats as everyone else in the family does and that extends well beyond salads.
What was helpful for us at diagnosis was to get into routines and stick to them. Ours was pretty rigid, which I don't necessarily recommend, but some level of consistency I do recommend. Caleb ate 50 carbs for every meal and ate them at the same time every day. I spoke with his endocrine team daily to review bgs and doses and make adjustments. Caleb's bgs were pretty fantastic with this method.
There are a lot of variables to consider when managing diabetes so the fewer you deal with at once, the easier it can be - thus my suggestion for consistency as much as possible to start. You will probably find that all carbohydrates do not respond the same for insulin dosing. For Caleb, pizza, french fries or ice cream are things we cannot just dose for because they impact his blood sugar over an extended period of time, different than bread, rice, potatoes, etc.
So although things will get easier as you identify and understand the different variables, it will always be something to juggle. I had the misunderstanding that when people said it would get easier or things would level out that things would be easy and his blood sugars would mostly be in range. It takes continued effort and reassessment, so don't think you're doing something wrong if you continue to see lows and highs, but it should be easier to deal with and manage and even expect at times.
Please continue to ask questions. I remember how isolated I felt and also how comforted I was by people I found online in communities like TuDiabetes.