There's a bug where one of the NPC's in my game is supposed to be marriagiable but the dialogue won't show up after I helped them and talked to the priest and wearing amulet of mara.

So I'm trying to do: Addtofaction 19809 1

but I don't think I have her targeted. Do I have to type the character base id? I don't understand how you "select" a person before console command, obviously talking to them doesn't work.

Normally in game you cant "target" any mobs, its just directional. But after the console is open you can target them. Just click the mob and its ID will appear at the top of the console.