Hi E.! I have two kids with DM1 and I want to tell you not to worry! The livestrong.com website that was suggested is a great help and so is the Calorie King website. I am definitely going to check out the site that Megan listed as well.
Your friend will be able to figure out carb counts, trust me. Any parent of a kid with DM1 is in carb bootcamp! :) You are so sweet to want it to be relaxing for your friend. Counting carbs, figuring insulin dosage, etc. is VERY stressful, and I say, good job! I mostly cook from scratch too, but I use my handy carb counting book as well as internet resources to find carb counts for each dish. It's really quite easy. If you have trouble, feel free to message me with a recipe and I can figure out the carb count per serving.
My husband also has DM1. Tell your friend that it's hard, but it WILL get easier to count carbs! My heart goes out to her! Many days (today, for example) are such a struggle.
As far as snacks go, always have some carb free snacks on hand. String cheese, pickles, olives, sliced meats, avocados etc. are "free foods". Avocados do have carbs, but they are rich in dietary fiber, which is subtracted from the carbs to get the actual carb count.
Hugs to your friend, and hugs to you too! Having a kiddo with a nut allergy is no walk in the park! I hope you guys have a fabulous getaway!