There are some dialects of American English that use that construction to mean that it has been a long time since the speaker last saw Nina. You probably shouldn't use that construction, instead say "I haven't seen you in a while."

That phrase is not correct. We would never say that. Instead we might say, "I have not seen you in a while" In a minute means that something will happen or we will do something very very soon i.e in one or two minutes.

It seems very unusual for someone to say "I haven't seen you in a minute." They probably meant they haven't seen them for a while and they're usually around all the time.