If they're going to make these "classifications" (which again, they shouldn't), then they need to adhere to their own rules. Their
own rules do
not say "must do amazing things." They say "a mutant whose dominant power is deemed to register -- or reach -- an undefinable upper limit of that power's specific classification." Marvel's own comics have repeatedly and explicitly said her powers are to such a level that by default, if Magneto's omega, then Lorna has to be too. No assessment of "feats" needed.
The list
also does not limit to only one person per category. Both Jean Grey and Quentin Quire are listed for Telepathy, so Lorna getting listed would not prevent Magneto from being listed. Objectively, Marvel's own rules say Lorna would have to be on the list even if they hate her. The only way the existing list could still work without Lorna on it is if it's a reflection of who
Xavier thinks should count, not who actually does count.
An ideal situation would be that Lorna's exclusion acted as an early hint that the whole concept of omega classification is bull and it'll be torn down later, but I don't see Marvel thinking that way. Marvel has a tendency to go full nostalgia and let all else suffer for it.
A read-between-the-lines addendum: this isn't really about "is she omega." Every character can be interesting if written right, regardless of "power level." It's about a clear and obvious discrepancy. Marvel's past comics explicitly say that wherever Magneto lands, Lorna also lands. If Magneto's alpha, then Lorna's alpha. If he's omega, then Lorna should be omega. Saying Magneto is omega while Lorna isn't exposes bias, adding to the pile of evidence that's been growing for decades. It's also a clear sign that such lists aren't to be trusted or respected, since they're just nostalgic fanboy inventions of whoever's running things at the company that day.