She lives in a tent next to the well until she's about to pop. Then Luthien shows up and the MC has Marcus renovate Ziva's old place for Liandra. If you never get her pregnant she'll remain at the well (and you have to keep having archery contests with her to get more sacred water).Was her home locked behind something? I think I'm normally mayor by that point, just not sure if it was a requirement. Liandra is one I keep neglecting, I tend to forget about her all tucked away in her little glade.
"Trouble At The Well" requires learning the Summon spell, so technically her & Luthien's questline is locked behind getting Erevi pregnant.