It is something she regrets, but has stated that she had very strong reasons for doing so.
And in today's Superman… you don't find out what those are. Not a clue.
Okay, maybe a small clue. Here's what I am thinking.
In today's Superman, someone does know Superman's identity. And is sending messages to Clark Kent revealing it.
And there it is. Danegeld. The principle that you have to keep paying and paying someone who has power over you, until you finally find a way to loose that grip.
Clark Kent wouldn't reveal his identity, because of those close to him, like Lois, that he might endanger as a result.
So Lois finds out. And won't stand for any of that. And she removes the grip this individual has over Clark by pulling the trigger.
And you know what? Despite the pain, the anguish, the terror…
He looks okay on it. Although that probably counts as "theft of services" Superman. And the difference is now that the airline will find it a lot easier to serve you wit papers now that they know where you live…
Comics courtesy of Orbital Comics, London. Who will be hosting a signing with Si Spurrier of his new Boom! comic The Spire next Wednesday from 6pm.