Getting a No shouldn't be the end all.
If you are 5'1" - 5'6" you have to understand the mindset of the industry. But beyond the agents you have to understand the client who is hiring the models.
Most of the time they are asking for a girl who is 5'7" because in the "mind" it sounds lean, tall, and perfect for their shoot. So they will call an agency and ask for all the girls who are brown hair ,etc, and 5'7" or taller. You won’t be asked to come to this casting of course. You won't even know it happened.
Remember being a petite model already means a challenge.
It is a short sighted industry so you have to push to get your self in the door.
Maybe your photos and your face or height were dissed but don't quit. Don't let ONE or TWO or one Hundred NO's hold you back. Instead focus on your photos. Being a petite model is like creating your own business. If you can impress an agent with your images, your height won’t be such an issue.
You need to start thinking beyond the norm, typically a shorter model becomes " another Internet Model" and forgets her real chances....Not just for hourly photo shoots where you wonder if you will get paid, but for modeling in ways that can get her ahead. It involves marketing yourself as a model and putting your best features forward. You might not ever be the model you want to be, but what about the model you are already? Are you considering all of the types of modeling, or are YOU also being narrow minded? Are your images making your look shorter? Are you not selling yourself with diversity? Are you only a sex pot, or are you also a girl who can model watches, handbags, and shoes?