A really good place to start is with the laws where she lives and where her studio is. The details will be different in each town, city, county, state and country. Its those details that can make a difference. Laws to consider:
1. What does the law say about storing your weapon? Some places don't care, some require them to be locked up, some require them to be unloaded, disassembled and locked up.
2. What does the law say about transporting your weapon?
3. Does the law allow you to even own the weapon?
The next set of laws to learn is the self defense laws where she lives.
1. When can you use lethal force?
2. When can you not use lethal force?
3. Do you have to retreat first?
4. Do you have "Stand your ground" laws? (look up what "Stand your ground" laws actually are... people's common understanding of them is incorrect)
Once all that is figured out... now the hard questions.
It may be legal to shoot the bad guy as he breaks down the door... but if / when I miss, will I be shooting into the living room of the house across the street? That is probably not legal. In some places, it is legal to use lethal force to protect property... if someone is destroying your car, on your property, it may be legal to shoot them, but are you ready and willing to deal with the consequences? Law enforcement will look into it, there may be grand jury or even trials, which means you need a lawyer. If you shoot, he may shoot back... You may shoot and kill him, and be legally cleared of any wrong doing... but you have to live with the fact that you killed someone over a possession.
Before I owned a weapon, I would put some serious thought into when I can use it and when I would use it. Note those may be very different answers. Also note that I am not saying anything political or anything about what the "right" answer is. Just giving you things to consider, that I think you should know before you get a weapon.
Also, yes, you do need to know how to use the weapon correctly, maintain the weapon correctly, store the weapon correctly and practice with the weapon. Know that you are responsible for the weapon. If you keep the weapon in a place that your kid or your friends kid or the next door neighbor kid finds it and uses it... you are responsible for that action as well.
I hope this helps. There is a lot to consider when owning a weapon.