Give the modeling agency a reason to want to work with you.
Show them you are more than just another model submission. Or face.
A shorter girl should bring some experience and ambition to the table.
If you want to know why there are not many short models out there it is because not many of them work hard and many of them give up and settle and don't really try.
You have to make the modeling agency want to work with you and it won't just take one photo submission, sometimes it can take 4-5 and it takes having some experience too, such as being in a magazine ahead of time, working with a few brands ahead of time and the pre-hustling of a girl who really wants to work in the business.
You should always be careful who you work with when striving to get your own tearsheets and work but if your goal is to get an agent always ask yourself,"How would the modeling agent think of this job?" Would the modeling agency I want to be with be impressed with this photo, situation or job?" If the answer is no don't do it. Don't be a fool, don't be desperate and be skeptical and careful.
However if you get some tearsheets, and show you can model, you might get a chance to work with a good agency but it does take work, and don't expect the whole " discovery! Moment." Understand that it is very challenging pursuit.