Unlike a girl of 5'10, a petite model is 5'1" or shorer- 5'6" and getting representation is a struggle. In all honesty breaking down the door and getting with an agency sometimes means adjusting your interests and goals. And being realistic with yourself.
If you go to an open call at a modeling agency and you get turned down, don't be mislead to think your chances are over or give up.
Start understanding what an agent is. A booker. Someone who has the connections and clients and who is marketing themselves too - Agencys are marketing themselves as a place to find the best of quality of models, and from their perspective they don't want to miss out a chance on getting a model booked because of her lack height when the client asked for a girl of 5'8 why is the agent going to send you? A girl of 5'1 or 5'4?
Sometimes you have to give the agency a reason to work with you, of course this means your photos need to be strong and you need to sell your personality and your availability and your energy as well. You might be 6 inches shorter than the models they usually work with but...
Are your pictures flattering and all have a commercial or editorial look?
Are you showing diversity in your images?
Do you have a nice clean headshot?
Do you have a nice lifestyle and body shot too?
Did you mention your on time and easy to work with?
Did you mention What you like about modeling and some jobs that might be perfect fit for you?
" I would be great for any casting you have that has to do with makeup or beauty because I have great eyes and even skin tone." Even if the agent is in front of you and can see this for his or her self, it is good to say it to bring out your positives right away, and let the height ...be an issue to forget!
Goodluck & Cheers!