Lucidstuck II

For it to be the Ue he'd have to know:

1) that lucia just woke and is prime time to impersonate her (which construct!alice supposedly doesn't know, and while we can guess/asume daydream does know, UE is from out of construct, so unless he's reading on spoilers or daydream -currently with emaily- somehow communicated it to him, he wouldn't know)
2) that she got a new fashion upgrade
3) gotten rid of Ira in some way to successfully pull this off (Ira, who last time we saw her was with reggie so if anything reggie would at least have seen what happened to her??)
4) how to get to LOMAM, when we've last seen it in LOHAM

Well,
1) UE can listen in on people a bit. We don't know to what extend but UE has some control over monsters, so it stands to reason that he knows what's going on around them. Lucia was surrounded by monsters when derrick woke up, so all she had to do was drop something about the big event that was coming up in her life and UE would know.
3)Ira's pasty enough that UE could've simply had some monster punch her to dream level 2. Or did it himself. Heck, he could've gotten her away with a ruse and by pretending to be one of the kids.
4)Bane has been watching Alice in locad because people were afraid of her getting impersonated by UE. Moreover, UE started out in derricks poster and managed to end up in loham. It's safe to assume he has some way of traveling between realms.

I don't have an explanation for why UE would know she changed looks. Perhaps he used vanity's trick to look into the real world? Or perhaps he just automatically has updated looks when he goes pretending to be one of the kids.

Either way, I still think calling reggie is the best option here, regardless of weither lucia's real.