Never seen her, though, I don't see anything that explicitly tells me this is a scam outside of her pictures being much nicer than your average backpage girl.  

 
She also has a cityvibe ad up, which generally points to being more legit than the average backpage poster, and her images come up clean when searched.

 
That being said, she's not that hot, and there are plenty of girls in SD that are hotter for not much more, if  any more, than what this rando nikki girl charges, but also have reviews so you know you're not walking into something sketchy.

Think with the big head...save yourself from anger and move on.