1. My girlfriend.
2. System error. It seems more like you're describing choosing between boring sex and interesting sex. It is not impossible for two people to be passionate about similar and common interests. There wouldn't be much of a connection or any chemistry without either.
3. Passion is nothing more than a strong feeling or emotion. Purpose is nothing more than an objective, an intention, a function, and essentially determination thus making it synonymous to "passion" entirely.