To me it's like asking, apart from do they exist, if intelligence is attractive ... which is as broad as asking if yellow is an attractive colour. If a girl uses her intelligence or colour coordination in a sexy, alluring manner, resulting in good service, the answer would seem to be yes. She could also use intelligence or colour in a neutral way or a downright insidious way. So who gives a fuck?
What happens I think is we look for signs that turn us on. Some of these we attribute to intelligence. Whether she's 'clever' enough to get a Ph.D., like the London prossie hero who wrote and published her diary and later became a highly respected scientist, who knows? -- and in Magnanti's case, we don't actually know , beyond what she tells us, if she used her intelligence attractively to the benefit of the punter, or not.
We used to have lots of students in Edinburgh prossying. If they claimed to be studying a subject I knew a little of, I might try to tell the difference as their honestly might make a more sensual bond. Most Edinburgh punters may remember Alexa, post-grad who even dared to use her University Halls student accommodation on occasion. Her intelligence was a slight plus factor to me as Uni students have to be good at listening accurately. I could rattle off a couple of complex role plays and ask her to pick one and trust her to remember and follow it exactly. I also decided she was trustworthy which is an entirely different feature and, unlike intelligence, also a quality.