From what I've heard on another forum, Peter David is playing it coy, but admits that yes, if you want Fallen Angel to be Linda Danvers, she is. I don't much see her being Supergirl in tone, but it's a pretty good read nonetheless.
I met Peter David at a comic-shop signing, back when DC's
Fallen Angel #1 had just come out.
He told a few people in the gathering there, that Lee is absolutely Linda Danvers and that the
Fallen Angel title is a direct continuation of the events from his last
Supergirl storyline. But he also said that he could never admit any of this in print anywhere or online anywhere and that he would always "officially" deny it. He will most likely continue to deny it on forums and in emails, but will probably do his absolute best to tell you the most that he can without breaking the rules - which is to admit that it could be "possible." So you have to read between the lines.
If you liked PAD's run on
Fallen Angel and you like his interpretation of the Linda Danvers/Lee character, I would say that she continues on in the new incarnation of that title. But if you like reading about a "Supergirl," then read the new DC
Supergirl title.
If DC ever does refer to the character again (which I really doubt, since in effect she's moved to a new publisher, just that no one can say it), it will in effect be a new character who will have splintered off from the "real" PAD Linda Danvers. She'll also have a new writer behind her. The only similarity will be that she'll have Lee's old name.