what classifies a woman to call herself a porn star?  how many vids does she do before using that title ?

A. There are very few real "stars" anymore. Mostly starlets or porn actresses.
B. I don't know the minimum number of works but it takes name recognition.
C. I also doubt you can just get there on solo. Probably require at least B/G or G/G.

Let's face it, if you aren't gonna take any dick in the videos you're in, you'd be a stretch for a porn star who's going to provide. I refer to the recent Jaime Hammer thread. Never taken a dick on film or photoshoot. Adult model sure, but not much of a porn star. You should be at least taking some play from toys (not just a little tickling or external use). Same thing with girl-girl. It's gonna have to be more than a little kissing and rubbing to qualify. I'm okay with the porn star label if you've gotten a small number of really good scenes, even if you've done it so you can market yourself as a porn star provider. Just harder these days to be a BIG porn star. Popular or with a good fan base, but its not like it used to be. Also just my 2 cents.

it amazes me that everyone seems to claim the moniker "porn star" these days.
it seems like one toe on webcam qualifies some.
my definition is to be a "star" you have to win an award.  
 i have done enough scenes to claim some place in the genre, but there is no category "adult film performer" or similar so i too grab the "porn star" placement. if there was another category like i  mentioned i would take it instead, but there is not

I've read that the majority of girls are in the biz of an average of a year. And yes, I've heard gals call themselves a porn star on their first shoot!  I don't think you'd consider an actress a movie star on the first shoot.  It takes time and a body of work.  And quite a few vids that say on the cover, "Starring___"