Hard to say, depends a lot on the severity. What you call nerdy and awkward girls (also applies to boys/people in general) could possibly have High Functioning Autism, which is considered the same thing as Aspergers Syndrome in recent medical science. These individuals have a hard time reading and communicating feelings and body language, hence the awkwardness. They often obsess over something, and can become highly proficient in that area. It is not rare that they score well in IQ tests.
If we move south on what is known as the Autism Spectrum, away from HFA/AS and towards classical or even severe Autism, things get more complicated. Reading and communicating feelings and body language can be hard to the point of impossibility, which most people likely would label as "retarded" or "unsettling", rather than "cute". Even basic communication by speech is harder. Obsessions tend to be more OCD-like and less productive the further down the spectrum we go, along with pummeling IQ scores. Predictability, patterns and repetition are very important to these individuals. They tend to do the same things over and over, and anything that is unfamiliar or which breaks the routine cause a lot of stress.
At its worst severity, and individual with Autism can barely function in society at all and require 24-7 care. Communication by speech is close to impossible, and therefore picture cards are often used where the caretaker looks for how the person with Autism reacts to it. Help with getting dressed, walking somewhere, or just visiting the toilet is required. If left alone for too long, self-harming behavior is a big risk.
Finally, pic related is mandatory reading for anyone who's interested in how HFA/AS works.