Hello there :) Haha why thank you for liking my music, I appreciate it greatly!
You’re my age, girl! You’re still growing - but exercise and a healthy diet is important if you want to lose or gain weight. I did calculate your BMI but, as you know, I am not an expert.

It says you are in the healthy weight range, which is GOOD!!! I don’t think that toning up, then sending in photos to an agency is stupid at all :) I think it’s a great idea! SOOOO many agencies are looking for “different” looking models, not just the generic types. I wish I was your height ALL THE TIME, I’m only 165cm - you’re very lucky :)
There are a lot of videos on YouTube that could help you out with toning your body such as Pop Pilates. I think squats are great for toning your bum/legs, but make sure you mix that in with some cardio or you won’t see any results. Start off s-l-o-w-l-y, don’t push yourself to hard at first! Try to incorporate more fruit and wholegrains in to your diet and try to stay clear of products filled with high sugar intake and salt etc…
As I’ve said, I’m not an expert. I just think that you’re a healthy weight but that there’s nothing wrong with wanting to look and feel better by exercising and slowly changing your eating habits :) Hope this helps! xo