there are exactly 4 and only recently. 2 sets of dead lesbians (because apparently someone at blizz thought "lets be progressive *scrolls through tv tropes* "ah kill your gays, that has 'gay' in it? this should work"
in Azsuna a ghost sends you on a quest to put her wife's spirit to rest. after you defeat the..satyr? ghost she returns to the quest giver and becomes a vendor.
On argus you come across the dead body of a lightforged woman. And if i remember correctly you bring it back to one of the main npcs and she asks you to check on her 'partner" who if i remember correctly you come across her body.
A few people have tried to shut up gay players by suggesting that the Red Smoke Pandaren guy was bi because blizzard failed to put in a different dialogue based on the gender of the player,
and there is the alleged attempt in the shrine of 7 stars. In which a human woman and a dwarf woman with the same last name blow kisses at each other.
its an obvious(ly bad) attempt to make them seem gay but as far as anyone knows they met there and thought it was funny they had the same last name (as happens in the real world) and joke with each other.
oh well i guess there is one more example. In the monk order hall there is a woman named after one of the developers, training, and another named after her wife cheering her on and getting Heart icons over her head.
so 2 background npc lesbians
2 alleged lesbians
and 4 dead lesbians