First, welcome to the club that no one wants to join. You and your daughter will be just fine. Living with Type 1 will become your new normal. Our son was diagnosed almost 13 years ago at age 10. It will get easier. I haven't read all the posts, but just off the top of my head, let me offer a few hints.
You will be given booklets and websites with carb counts. Use these to compile your own little book of your daughter's favorite foods. Keep one in the kitchen and one in her D bag, so you don't have to keep looking the same foods up, until you learn them, and you will learn them and soon even be able to eyeball foods that you can't measure when away from home. We still measure some foods. Have plenty of measuring cups and spoons handy. We've never used one, but some people even invest in a good scale. Some foods are harder to cover with insulin than others. You will learn this by trial and error.
You will need to keep good records, especially in the beginning. You will be asked to bring them with you to the endo's visit. You may be asked to bring a record of blood sugars and food log. Find one that works for you. The ones we were first given were so tiny. I couldn't squeeze everything on them. Use a notebook, or make your own forms. We also use a dry erase board with color coded markers. It helps when looking for blood sugar patterns.
Learn everything you can, and do what works for you. Ds has never had a pump and doesn't want one.
Puberty is wild! You will survive. Sick days are tough, but knowledge is power.
We homeschooled, so I never dealt with school nurses. I would strongly recommend you work with your school and get a care plan on file as soon as possible. I can't remember the name...Section 504???? Someone here may be able to help you with this.
For my son, sometimes opening a new bottle of insulin will cause us to have to adjust dosages.
Don't make a big deal of blood sugar readings with your daughter. My son would often apologize for numbers out of target range, which would break my heart. Make sure she understands that it's not her fault. The only consistent thing about Type 1 is its inconsistency. :)
Finally, and the hardest thing to admit...is you can't control this. You can manage it, but you can't control it. There are so many things that affect blood sugars, not just food. Physical activity, stress, excitement, illness all affect blood sugars. Some people's numbers will shoot up during early morning hours. Some people drop during the night. Most of the time, you will get the numbers you are expecting. Sometimes, you will get a number out of nowhere. You daughter can eat the exact same foods every day at the exact same time and have very different numbers from day to day. You can't control it, but you can adjust and give corrections.
We finished our homeschooling journey years ago. I don't post, but still read the boards. I'd be happy to answer any questions.