If you are a petite girl and you want to model you really need to be a few things that have nothing to do with the "modeling" thing, to get an agency and to get work as a model.
#1. Be able to market yourself, and know how to. This means knowing how to approach agencies and not being afraid to. Tip: Sending a smile shot to a commercial print modeling agencies and do not mail half naked amatuer photos and fashion shots. A shorter model needs to understand that her personality has to come into play to get a commercial print modeling agency working with her.
#2. She has to have a marketing mindset and think about the way she markets herself, and creates her compcard and headshot. A lot of being a model and working in the entertainment business is like working in the advertising business you have to know how to put together a portfolio, compcard, and resume that best represents you.
#3. Although modeling is about holding a pose and using your look, and self to represent a brands image and the concept for an ad campaign, it also involves being perceptive and knowing how to relate a concept to yourself and make the shot, pose, theme for the shot look natural.
#4 It is important to know how to get the job done but also not forget that you as a person should not ONLY be defined by one thing. And modeling should not be the only one thing that you want to be and that defines you.
If you do not have a marketing ability and you are not confident then you should re-think modeling. Today modeling when you are a shorter girl really has a lot to do with smart, savvy and realistic self promotion. Putting together your marketing materials and making what you want to happen to happen by research, persistance and trying. There is a big difference between a girl "wanting to be seen and call herself a model," and "being one."