It doesn't matter how old/young you are, it depends on your height, if you're in shape and your size/weight ratio to the other flyers on the team. Even more important is your experience as a flyer. If you're on a level 4 - level 6 team, you're going to need to have experience, as they do very complex stunting, but if you're level 3 or below, then I am sure you would do fine, as those levels are more beginner. I would talk to your coach and express your interest. I am 5 ft as well and was a flyer for 12 years on my all-star cheer teams, and one day decided I was tired of flying so I asked my coach is I could base and she let me. Luckily, there were two more flyer's who were smaller than me so it just worked out.
Start stretching and balancing so you can show your coach your skills when she asks to see what you can do. I bought something called a "Mayflyer" which was specifically for flyers and practicing their balance while doing stretches, libs, scorpions, etc. It was way harder to balance on that than it was in a stunt where people are holding your feet, so it was perfect for practicing.
Just practice and talk to your coach. That will be your best bet. Good luck :)