She would have gotten the dose, it's fine.
It can be administered directly into the blood stream so no need to worry there either.
It sometimes happens where you hit a blood vessel. I done this once in practice and panicked as it was a drug that can't be given intravenously. (Ideally it's subcutaneous though)
When you next inject tomorrow, just pull he plunger back slightly before pushing the plunger down to administer the drug. If you get a lot of air, you've gone through the skin. If you get blood you've gone into a vein. If you're in the right place the plunger will pull itself back to starting position before you inject.
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