Her powers were restored by Celestial technology, but more then a few people confused about that and believed she had machines giving her power like Iron Man only even more internally. That was never actually stated, just something inferred by some fans based on some uncertain comments on the matter in the year or so after.
Just remember Magneto's powers were artificially restored by Celestial technology too. The writers didn't do that on accident as that was the technology that created mutants in the first place, but the writers were working around editorial restrictions of no new mutants period so they were 'repowered', but it was a few years before they could be 'confirmed to be mutants' again.
Lorna was confirmed as a mutant as was Magneto by Cerebra in X-Men Legacy in 2011 as if you have an X-gene you are a mutant.
But, I appreciate it when fans ask questions about something they are unsure of.
In the end Lorna being a mutant really hasn't mattered from M-Day to now and for a character sort of custom built towards the political side of mutant affairs being divorced from mutant politics and mutant issues for the longest time since Claremont’s run. If she was a human powered by a machine like Tony Stark or a mutant it wouldn't have mattered.
We will see if this ends up being the first year since 2005 her mutant identity actually matters again.