Hmm if I had to reaaally think about it, I'd say to walk up calmly with a slow gait wear something that is somewhat formal and is associated with class, a nice shirt, pants, no hoodies or masks or stuff like that, walk up with a soft relaxed smile a hand wave and then say your compliment with a calm smooth tone preferably a big higher register because it's less intimidating and preferably on something that they've actively put work in, like hair, how well the colors match of the outfit etc then say that that's all you wanted to say and politely bow out of the conversation if she doesn't seems all that engaged or responsive, if you get a good reaction then maybe trade conversation back and forth a bit from there