im not quite sure how small you are looking for but my colt was 37 inches at birth, that's basically 94 CM. However his mom was only 144cm tall. He has since grown to be 14.3 hands at the moment, if I am thinking correctly that's about 145 centimeters, and he is only 2 years old. Most horses grow and fill out until their 5th or 6th year, you may not be able to ride her at 2 or 3, but give her a good while to fill out completely I am sure she will grow big enough for you to ride.
Baby, Sparta, Carmen, Henry, Hooch, Mercedes, Butterscotch