Well, I say this because at the end she "sences" the flower girl.
And we dont really know about Dyne's wife, only her name.
So???
Hmm, I wouldn't think so. The other girl in AC referred to Aerith too (the one showed holding the Moogle doll) and I doubt there are that many Ancients running around the world.
I think it's a matter of some children being able to sense Aerith more clearly than adults, probably because their minds aren't filled with the worldly troubles of reality. And because Marlene was very close to Aerith in the short time they knew each other.
Also, Marlene never once mentions hearing voices from the Planet or sensing spirits other than Aerith's.
I agree with Lynn. It seems that Marlene can sense her because she's a child, since that other child also hears Aerith. Aerith is seen kneeling next to those other two children near the entrance to the Temple, too.
On top of that, Cloud can see, hear, and touch Aerith in AC... yet he's not an Ancient. I suspect that Cloud is able to because of the strong bond of love he had with Aerith, but I believe that Marlene can simply because she is a child.
I've always liked the idea of Marlene being an Anicent, but Lynn's points pretty much refute that.