Keljonma it sometimes seems like "when it rains it pours" doesnt it? What makes it worse is that there is nothing you can do. If they were your children, you would just deal with it, ya know? But since you are "grandma" all you can do is sit back and think.....and think.....and wait and worry. Sucks. I know. With three granddaughters and another grandchild on the way, boy do I know.
My shots all have to be rotated. One in each arm, one in each side of the hip, one in each thigh and one in different sides of the stomache. If your granddaughter is on the thinner side (all of mine are lol) that might be why she has to have it elsewhere and not in her arm. They may need thefatty tissue. Do you know whether it is sub cutaneous or intra muscular? If it is sub cutaneous then they need the fatty tissue. If it is Intra muscular (spelling?) then they need a larger muscle than the arm.
I feel for you. Take care.