Many vets start with insulin once a day. This is so the family can get used to giving it and the vet can see how the pet responds to it. Ultimately almost all dogs need it twice a day. Most dogs don't mind it. In long haired dogs, it can be helpful to shave a couple of small spots to help to access the skin. Ideally the injections sites should be rotated every day.
Your friend should get a glucometer and ask her vet how to obtain the blood. Most pharmacies will give the glucometer for free because they make money on the strips. Being able to test blood glucose at home takes a lot of guess work out of administering insulin. Continuous glucose monitors can be used in dogs, but right now the units are cost prohibitive for most families (about $1500 for the unit & $40 for the probes) but they will probably have their place in the future.
Dogs are always type I diabetics and there is no chance for remission like there is in cats who are usually type II.
It is very important to get glucose control quickly in dogs because they are very prone to diabetic cataracts and can go blind almost overnight. The cataracts can be removed to restore vision, but the surgery is several thousand dollars.
Hypoglycemic episodes in dogs are not as common in cats. If they happen, your friend would notice her dog to be "spaced out", then start the become weak, tremble, fall down & even seizure. Administering corn syrup on the gums and getting the dog to the vet quickly usually allows a fast recovery. This is also where the glucometer at home is important. If the dog is closely observed & just seems "off" she can get a glucose result in seconds and know if intervention is needed before things get bad.
Diet & feeding schedules are important. She needs to ask her vet what they recommend.
Most dogs are on caninsulin/vetinsulin. It requires a U-40 syringe which is not available in human pharmacies. If she does use a U-100 syringe, she must convert the dose. People try to save money by re-using syringes but it's not a good idea. The needles are very fine, get dulled going through the vial's stopper, get dull again going through the skin and dull needles are harder to use and cause more pain. There is always the potential for contaminating the insulin with skin bacteria also. Your friend can get a small hazardous waste container from her vet & return the used syringes to them.
As a nurse, your friend probably knows the importance of handling insulin: temperature, re-suspending the insulin crystals gently etc.
Many dogs have a concurrent bacterial urinary tract infection when diagnosed because of the sugar in the urine. She should have a urine culture done because any infection in the body can cause interference with glucose control.
The last thing I would add is that there is a lot of information on diabetic dogs on the internet --good & bad. Here is a good place to start:
http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=631. It is written for the public by veterinarians.
I hope everything goes well for your friend & her pup!