In your opinion, why did some survive the holocaust?

Wow.... that's a question.

You know there are a million answers for this, and I think a lot of other people will add to this, and still not cover all of them.

The ones I can think of right now are:

Timing: If you were incarcerated in a death camp shortly before the allies came, you had a better chance.

health/strength: if you were healthy, and could hang in there long enough to survive the ordeal you might have survived. I would say this is a gross minority, not too many people retained their health.

marketable assets: if you were able to convince the powers that were that you had something thye could use, maybe they would keep you alive awhile. Some managed to survive long enough to make it.

Stealth: Some managed to stay under the radar, kept a low profile, or maybe God willing managed to escape before it got really bad.

Those are the things that come to mind immediately. There are many more, I would think.

Part of your question I don't understand. I don't think anyone would survive a bullet to the head, under those conditions or any other.

the bullet/shot does not hit the critical/fatal point on her head.

Luck, adaptiveness, and divine intervention. Although if divine intervention were a factor, it was probably a little late. Why not intervene in 1938 and save them all?

Read "Survival in Auschwitz" by Primo Levi. Survival was circumstance, and he lived through it only to suffer massive depression and kill himself. No body really survived, they just were not killed.