Being robbed and beaten up is pretty unlikely - I wouldn't worry too much about that.
As it's your first time, you will be nervous and rightly so...to be honest, for a first time I'd recommend going with someone well reviewed, but each to their own.
Be prepared to walk if you aren't happy...ok, she might not look quite like the pics but if she is still decent, I expect you will go through with it. However, if she looks nothing like her then make your excuses and leave (left your wallet in the car, realised you don't have enough cash so nipping to the cashpoint etc). It's difficult but a good skill to have (I've never done it, and probably should have)