Hello. Newbie here.

Hello everyone. I'm Jamie and I'm trying to lose a bit fat in order to start building (back) a bit of muscle for health and fitness. Currently I am 170 cm (5'7") and weigh 56.4 kgs (125lbs). I'm doing the 1200 kcal/day thing and will start my weekday swimming routine next week or so when school starts. My goal is to reach 50 kgs and then start to build muscle, probably gaining up to 55 kgs. Any advice?
Oh, and I used to do triathlons back in seventh grade and played soccer. Just wanted to go back to that before I go to college next year. I'm female, by the way.
One last thing. I'm Taiwanese. Any Taiwanese people around here? :)