I reunited them before I picked up the decanter and now Aelwyn is still in the same place but I cant find Nemelle anywhere. Am I gonna just have to carry on without Ignus?

In theory Nemelle should have joined Aelwyn. Both should be at the Cafe. Start there. But for some reason she seems to wander around and can be nearly impossible to find (like hidden "behind" the roof of one building). Good luck finding her in that case, you might choose to ignore Ignus rahter than exploring each inch of the map.

When you said you "reunited" them, did you actually talk to Nemelle after she met up with Aelwyn, or has she yet to arrive there? If the latter, just wait by Aelwyn for a few minutes while Nemelle walks over.

Well..she randomly appeared by the bar again after a long time. Thanks for the help anyway guys!