I'm not sure I buy the explanation that Luthor's infant daughter Lena was retconned into being his adult sister Lena.
There was already a "Luthor's sister Lena" counterpart in Post-Crisis continuity; his dead foster-sister whom Baby Lena was named after. There's no reason why she couldn't have been named after a living sister, and there's no indication these stories didn't happen post-Infinite Crisis, beyond the fact she never gets mentioned. (The DC wiki lists the two Lenas as niece and aunt, so they think they co-existed.)
In any event, Baby Lena makes her last appearance more than a year before Infnite Crisis, and is notably absent from the Superman/Batman story that closed out the Luthor presidency, so being retconned out in IC (whether or not she "turns into" the older Lena) doesn't explain where she went before that.
I'm not sure I buy the explanation that Luthor's infant daughter Lena was retconned into being his adult sister Lena.
There was already a "Luthor's sister Lena" counterpart in Post-Crisis continuity; his dead foster-sister whom Baby Lena was named after. There's no reason why she couldn't have been named after a living sister, and there's no indication these stories didn't happen post-Infinite Crisis, beyond the fact she never gets mentioned. (The DC wiki lists the two Lenas as niece and aunt, so they think they co-existed.)
In any event, Baby Lena makes her last appearance more than a year before Infnite Crisis, and is notably absent from the Superman/Batman story that closed out the Luthor presidency, so being retconned out in IC (whether or not she "turns into" the older Lena) doesn't explain where she went before that.