Education is the best defense. If you are near the pacific NW message me or email me, I'm a licensed security guard (armed and unarmed in wa & or and unarmed in va), i've done fugitive retrieval, Navy, and protective escorting. I'm always happy to offer free training and advice if it keeps people safe from attack, and keeps them from buying a gun and hurting someone else with it cause they don't have a clue (gun owners have enough trouble already).
As an RN she will be forbidden from bringing any weapon into her workplace under most federal and state laws. Most hospitals do allow personal defense weapons like sprays as long as they're never seen. Aside from that every weapon REQUIRES serious training to be effective. Lack of training is going to get her hurt far worse than no weapon at all.
If you're not close enough for me to help you, call the police department and ask for pamphlets or training videos/classes. Look around for a good martial arts school (don't have to become a black belt, just get some advice). Call security companies and ask them to recommend local programs.
Safety should never be taken lightly, it's a dangerous world.