I have been opening and closing with a high success rate for about a year now, but a few days ago I met a shot girl in a local club, and I froze up. This is the second time I have frozen up on a girl in my life. Her hotness matched with her fast-paced work makes it really hard to get and hold her attention. Any advice?

When it comes to shot girls/ PR's/ Reps you actually have a slight advantage.
It's HER job to hold your attention as shes not only trying to sell you something but also sell herself to get you interested enough to buy.
the majority of the time the technique i use is to never buy what she is selling but to neg her by making her think you may be interested.
you can outright say with a blunt straight face 'nah sorry not interested and begin to turn around'
as she go's to turn and leave you can swing back around with a cocky'funny grin and initiate contact with a grab of the hand.
say something like 'Oh come on your not gonna make it that easy are you? sell it to me, give me your pitch!'
from here she will either start to give you her pitch which after you can playfully say 'well that was awful! and give some pointers.
Or she will say she doesn't want to pitch in which case you can say 'well your not very good at this are you? are you new?
This has a very high success rate for me as it leads on to a comfortable position where you can get as cocky'funny as you want.
I even escalate to the point where i take a shot and hold the bottom in my mouth while egging her to take the shot from the other end.
Just remember SHE needs YOU