I noticed that Mehra Milo is not scripted to teleport from the library to the Minstry of truth to Hlormaren but she manages it. I'm assume there's some command in the dialogue that transports her. Can anyone tell me what it is so I can try it with my own mods?

It seems she is moved to Holamayan by the script "MoveMehra", which is presumably started in dialogue by the line "Startscript MoveMehra".

You were right about a "teleport" command being done by dialogue, though - she is moved to the Ministry of Truth by a line in the "Orders" topic, by Caius Cosades:

"Mehra Milo"->PositionCell, -680, -363, 88, 270, "Ministry of Truth, Holding Cells"

Having "the same" NPC appear in different places can also easily be done by using two cloned NOC's. One in one spot and the other in the other place (completely redundant sentence). Then manage this by using basic enabling/disabling scripts that control when one appears and the other appears. That way you can also tightly control dialogue that comes up.

Thanks that helped a lot