I have seen this in some ads and I'm not sure what it stands for. What is PSE?

Unfortunately it's just as hard to define as GFE in most cases.  The translation is Porn Star Experience.  Does that mean its more business like and less girlfriend like? Maybe. Does it mean that she'll DT and get very sloppy with her bjs? Maybe. Not all porn is sloppy - thank God!  Does it mean she'll go greek? Maybe. Also remember that there are many porn stars in this hobby and they might not do these things either.  Maybe it will mean that she'll get nasty and say all the things you wish your girlfriend said in the bedroom, maybe it will be the most athletic fuck of your life.  Unfortunately there is no true definition that we can rely on, you'll have to ask the lady in question or PM the reviewer to see what his definition was at the time.

I think this definition is good.  See link for more.

PSE's may be more active, more vocal, and more aggressive, like in Porn movies.