When a girl calls you "handsome," it generally means she finds you physically attractive. It's a compliment that suggests she likes your appearance and thinks you have attractive features. The term "handsome" is often used to describe men who are good-looking, charming, and pleasing to the eye.
This compliment can come from someone who is interested in you romantically or simply admires your looks without any romantic intentions. It's a positive and flattering remark that many people use to express their admiration for someone's physical appearance.
Keep in mind that compliments like these can be given with different intentions, and it's essential to consider the context and the person's body language and behavior to gauge whether they are interested in you beyond just a compliment. If you're interested in the girl as well, this might be a good opportunity to engage in conversation and get to know each other better.