is there a flirt pack for NWN?

Not that I know of and I don't think there'll be. From a module builder's view, I'd say there are few too many people replaying OCs to make it work or get really the credit you deserve. Also the campaigns are so hard to edit if you don't know how it's build, what is where. Even if I can find a good example in it I wouldn't take an OC as first source of info cause they're so complicately scripted (not as in hard but as in cross-referencing to lots of other different scripts, which would be really tough to get much inbetween)

What is a "flirt pack" anyway?

could be like the bg2 flirt pack i guess

A custom extension to the game that makes NPC romanceable or more NPCs romanceable

Mods do you know if there is a flirt pack.

I searched the vault for it and there is none. Your best bet would be searching a module that uses custom henchmen that flirt. There seem to be a few modules that at least have henchmen with a lot of dialogue, though I don't think all will have flirt/love options. But I haven't tried a lot so you should ask someone else.

The Shadowlord/Dreamcatcher series of modules have romanceable Henchmen and are excellent all around.

thanks you 4 your time