I don't think she was supposed to be there. There was speculation that one of the Force Warriors was her but as it turned out, it was Unuscione instead. I don't recall seeing anyone that looked like her there.

Nightmare's "Bio"?  Where was Wind Dancer mentioned???

This is Nightmare's Age of X Communique:

CIVILIAN NAME
Megan Gwynn

KNOWN RELATIVES
Owen and Brenda Gwynn
Grandparents. Dead.
Possibly related to Jason Wyngarde (Mastermind): DNA comparison was suggestive, but inconclusive.

COMMENTS
Gwynn was born in Wales, and there’s ample reason to wish she’d stayed there. She and her grandparents were part of a general expulsion of X-gene positives from the United Kingdom, with the apparent intention of settling them on a series of small islands in the Irish Sea.

That plan became moot when Irish separatists bombed one of the ships carrying the transportees, and the others turned back. The Mutant Liberation Front seized control of the ship carrying Gwynn (we believe it also numbered Jonathon Starsmore and Elizabeth Braddock among its passengers) and ultimately were able to berth it at the Canadian port of Saguenay.

Gwynn was as green as grass when she arrived, and was one of many mutants recruited, groomed and trained by East Coast mafia crime families. It’s known beyond doubt that she served the Carcotti organization as a runner and enforcer. Must have been quite a culture shock for a kid brought up in the Welsh valleys, but – obviously – she survived and thrived in that Darwinian environment.

Fun fact: Gwynn used to have butterfly wings, and went by the nausea-inducing pseudonym of Pixie. Her current shoulder accessories are more demonic in nature, and apparently they arrived on the night of the Bleecker Street Massacre (qv). As far as we know, Gwynn hadn’t killed anyone up to that point. God knows, she’s making up for lost time now.    

Sofia wasn't involved in Age of X because she wasn't on Utopia when 'Moira' transformed reality.  As ComicMan24 said, there were a lot of rumours that she might be in it.  Fan were expecting her to be in it because the character design for Unuscione looked remarkably look a grittier Sofia.  However, she was NOT in the Age of X.

She wasn't in nightmare's bio, she was in Hellion's. 

HELLION

CIVILIAN NAME
Julian Keller

KNOWN RELATIVES
William and Elizabeth Keller. Parents. Serving life terms at Lompoc federal prison for harboring a mutant. Elizabeth identified as X-gene bearer and sterilized.
James. Brother. Dead (see Operation Clean-Sweep).

COMMENTS
Keller came from a rich family – new money, but plenty of it. That probably helped him to stay off our radar for as long as he did, although former West Coast Director Robert Monahan was certainly both unwise and premature when he declared the Western seaboard mutant-free.

Keller might have evaded capture for many years longer if it hadn’t been for his own arrogance. He allowed himself to be seen at Los clubs and restaurants, and maintained a highly distinctive 1967 Chevrolet Camaro. Following that trail without undue difficulty, MRD investigators found that Keller had been living for a year and a half in a bespoke underground shelter fitted out to luxurious standards.

The next sentence ought to read: “and that shelter became his burial mound.” However, the field officer assigned to the operation wholly underestimated Keller’s telekinetic powers. A laser attack intended to kill him instantly, before he even knew an attack was imminent, succeeded only in severing his hands and forearms. Keller was able to stanch the flow of blood telekinetically, and tore his way through the attacking Exonims to effect an audacious escape. Three jet fighters pursued him: the largest piece of metal obtained from the subsequent wreckage measures seven millimeters.

Keller was one of the last mutants to make his way to Fortress X, having by that time survived on his own resources for three years. He was part of no resistance group, was sheltered by no pro-mutant agencies and made contact with no foreign sympathizers. He seems to have made a point of pride out of not accepting any help from others.

It’s not known what finally brought him to respond to Magneto’s call. Perhaps he reached the limits of his own sturdy self-reliance. Or it could be that Megan Gwynn (see below) had a hand in recruiting him, as she’s known to have done for Sofia Mantega and Sidney Green.

 
 
This goes under the category of 'big whoop'.  So she's mentioned, so what?  Copycat is mentioned in Cannonball's X-Communique, and in Beserker's it says that he has a half-sister which he didn't have in mainstream reality.  The fact that Sofia is mentioned doesn't mean that she had to appear.