A few things... The quest you get in the Inn isn't related to Jaheria's main quest so you won't have to complete that to continue the romance and eventually finish Jaheria's quest/romance.
And if your not in a romance with Jaheria you don't need to rest outside in the wilderness as the Harper's will approach you after doing Xzars quest.
So lets sumarrise what is to be done to activate the Jaheria harper quest note this conatains *SPOILERS*
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1)When you leave the city for the first time or if you spend alot of time traveling about the districts before you leave you will be waylaid by a group of bandits. Kill them and take the poisoned man you find there to the Harpers building in Athkatla.
2)After you give them the poisoned man Xzar will approach you with a quest. Complete it.
3)After if your not in a romance with anybody a Harper will aproach you and THE HARPER QUESTS WILL BEGIN, YAY!
4)If you are in a romance with Jaheria complete steps 1 + 2. But the Harper won't approach you as some requirements in the romance have to be made. After a certain dialog in the romance you must rest outside and something interesting will happen(trying not to spoil here). Once this has finished the Harper will approach you and THE HARPER QUESTS WILL BEGIN, YAY!
Note: I forget exactly after which dialog you must rest outside just try it requarly or if you haven't had a dialog for a long time that could be the indicator it's time to rest outside...