Enjoy the time and focus less on the act itself. Hopefully you have better results the next time.

You shouldn't (I know easier said than done) be embarrassed, but instead share with her your anxiety and trust that being she is a professional, she will ease your concerns.

she might even take it as a the most genuine possible compliment.

Re: If she WAS that gorgeous

I'm sure this happens to her all the time...
CALL her again, i'm sure she could have cared less if this happened, and she doesn't think anything bad about you..CALL her again, and maybe masturbate before you get to her, it might help
Jay

You don't say what happened next...  How did she handle it?  As has been suggested, a good provider probably has had it happen before.  You still had time on the clock...  a quick clean up & start over...  
Maybe not exactly the same but all of us have been surprised at one time or another.  Recently, I had the surprise to give my partner a handful unexpectedly!  We thought we were just warming up.  So there was more to do, a quick clean up & try something else.  There have been other times...  Sex play does have an element of unpredictability...  
Unfortunately I'm not able to recover within a reasonable time...  but many are able to cumm again.  My Fav had a lot of fun getting me back up...    
skb

AND you really like this woman. I would suggest that you not only rebook, but that you book for a longer time period. Book enough time for you to recharge and have a longer more enjoyable second course.

One other word of advive, the surest cure for PE is sex, a LOT of sex. Save your money if necessary and have sex four or five times a day for a day or two. Sex will lose some of its mystery and your control will increase ten fold. It's not as expensive as you would think, schedule four appointments 6 hours apart.Two days @$250 a session equals Two Grand. Trust me, it will work wonders at a fraction of the cost of "therapy".