Hi Kayla! Umm, don't go for HGH yet - it has really bad side effects if haphazardly taken in. You're still young at 15 years old and you have like, a five to seven year window for growing tall. You'll probably reach a minimum of 5'9 by the time you're 18. Just concentrate on living a healthy lifestyle right now - and once again, avoid the HGH - it may do more harm than good.
If you need tips, here are the cool stuff that I got from waysgrowtallerfaster.com blog:
1. Eat a healthy diet. Get enough calcium, protein and fiber. Don't count out vitamins as well. I know you want to be a model, but don't starve since it may cause your growth to get stunted!
2. Exercise. In order to negate the effects of too much calories, try exercising. It'll strengthen the bones and muscles as well. Remember though, avoid weightlifting and only try out jogging and non-contact sports!
3. Get enough sleep. Eight to ten hours per day would suffice.
4. Avoid anything that may stunt your growth, like smoking, liquor, drugs and other dangerous substances.
5. Don't stress yourself out just yet. Enjoy life with your friends, family and just about everyone you know and love. Getting rid of stress is one step to achieve a healthy lifestyle :)
Last tip: go for what you want. Don't let other people discourage you from reaching your dream. Just be determined, be positive, follow my tips and you will be fine. I really wish you good health and more opportunities. I hope your dream will come true :) I really do.