You begin to have a teeny-tiny idea of what it's like to be the only woman in a large group of men.
The following are some guidelines for complimenting anyone:
You almost certainly shouldn't compliment her on her hair, her face, her body, or her sweet temperament. If she's interested in Linux, she is, by definition, a geek, and probably wants to be complimented on her intelligence, abilities, and hard work. Compliment her on installing Linux for the first time, on her customized desktop, on her intelligent and interesting questions during the last meeting. A compliment on anything else is inappropriate and will be seen as a sexual advance (because it almost always is), and will make her feel more uncomfortable and less confident.