I believe if you want something you have to do the work, research and put in the time to make it happen.
A lot of girls want to model, but modeling has a lot to do with marketing and there is a lot involved with being a model, getting work, and working with agents. Getting work in print magazines, and working with top brands that everyone knows. For a shorter girl the Gucci type of ads and modeling should not be on the mind, the best way for a shorter girl to model is to think about lifestyle products and brands and to target, create and produce photos that best show her personality and that she has great energy and a welcoming friendly smile.
Then comes the marketing. You have to send your photos out to agencies first and really do some work ahead of time. How do you get a modeling agent? You have to mail them your photos, your smile, headshot, ect, and hope they call. How long might it take? Weeks. After a month if you don't hear back I would keep hustling, keep working on images. It could be your images, not YOU. So you should really keep trying to improve your headshots and remember a smile shot in the commercial print modeling world is what you need. Not a Vogued out fashion shot.
So if you do not have an agent maybe:
1. You are sending the wrong photos to the agents/agencies, that do NOT show what they want to see. A commercial print modeling agency, talent agency wants to see your smile.
2. Maybe you are not sending your photos to the right agencies. Are you only sending photos/compcard to fashion agencies? You should be sending them to print modeling agencies because in print there is usually a more flexible height requirement and girls of a shorter height can find modeling acceptance here.
3. Really trying. I believe if you want something you have to do the work, research and put in the time to make it happen. With that said, remember that one modeling submission to an agency, or agencies is not enough. You might need to make more than one submission and you should.
Believe in the power of you. Take it upon yourself to make what you want to happen and be smart about it. A lot of modeling has to do with marketing. How you present yourself and how much you want something.