It was only <for> luck she didn't die

[NAL123]

1) The bike hit her really hard. It was only luck she didn't die.

2) The bike hit her really hard. It was only for luck she didn't die.

Which is correct? And what about:

3) The bike hit her really hard. It was only because of luck she didn't die.

 

[jutfrank]

It was only by sheer luck that she didn't die.

 

[Tarheel]

Or:

She was lucky to survive.