First off, no 15 year old should be drinking, especially not the stonger stuff like vodka.

How did she get it in the first place?

What will 2x750ml bottles do?

Depends on the person. I did it at a friend's wedding without side effects, but was also eating a lot of food to help offset it, was 23 and healthy at the time.

Inhaling deodorant will probably induce vomiting, if not worse.

Here is what I want to know, and you to think about:

Why weren't you there to make sure things didn't get out of control? If you were there, why didn't you or anyone else do something about it before she got drunk? Alcohol is a depressent / poison even if she survives she will probably be in bad shape for awhile and having such a high tolerance usually means one is becoming, or is, an alcoholic.

Not even adults should consume so much alcohol w/out having someone there present in case something would go wrong. (And believe me, 99% of the time, it does.)