I really don't know what to make of Alice's expression. As an artist, this is one of those things that might not hit me until render time. Alice is "thousands" of years old. What does fear mean to a person like that? Has she seen this before?
Over analysis be over analysing, but I suspect she has. She doesn't really strike me as very afraid. Just concerned. Which would imply that this is something dangerous, but not so dangerous that can't deal with it. Which would suggest, to me, that any concern is either about containing it so that it doesn't spread, or about protecting Ardent. Or both.
That she is focused on removing Ardent from town would suggest, assuming this is something she's seen before, that the power fountain is basically harmless. It isn't going to spread, or if it can, it would be so slow as to be something for manana. That she wasn't to ask questions of Ardent would suggest, assuming she's seen this before, that she doesn't have an immediate plan to protect him from the thing she is concerned about. This would suggest two further possibilities. One, the thing is a danger to Ardent and she is worried that she might not be able to anything about it. Two, the thing is a danger to everyone, and the one sure way she has to stop it would be fatal to Ardent.
I'm leaning toward the latter cases, simply because Jeph may not get perfect pacing, but he knows story. He didn't need to end the infodump gag with a line implying that Alice is growing fond of the kids. He could have put any gag there. Like I said, overanalysis, but Ardent and Gavia are, I think, now inside Alice's "mine" mental map, and she protects what she lays claim to.
I think that she's concerned because to protect Ardent, she might have to kill him. (Obv's I don't think that's going to happen, but I think that's where her state of mind is, right now.) If whatever force that she knows should have made it (flatly) impossible for the kids to be on Earth, I'd have expected her to be more shocked that they are. She thought Ardent was a con, at first, which suggests means to being blue and pointy are available on Earth (My bet is that blink separated the biotechies from the techies). But when it became clear it wasn't a con, she didn't really bat an eye.
She is old. I suspect that means she is hard to really surprise, and when she is surprised it hardly shows for long. Because there's very little she hasn't seen.
Again, could be totally wrong, and just looking at the whole thing from a perspective Jeph didn't. But Alice really does see the town as hers and she really does protect her stuff. If the pump was the source, she'd be doing everything to isolate it. So either it isn't, or she doesn't see it as a threat.