As YCBM says - its how long is a peice of string! It partly depends on how long your legs are in relation to your torso than your overall height - and partly on what you feel most comfortable on. You could fit neatly onto pretty much anything from about 13hh to 16hh. You might look a bit oversized on something below 13hh - but a native that takes up a good length of leg would still be OK. You might feel a bit too far off the ground on anything over 16hh given that you seem relatively inexperienced. A larger horse might have a larger movement which can unsettle a novice; a smaller pony might have a daisy cutter type action which can be jarring. Both are generalisations of course - you see ponies with a really extravgant movement and vice versa.
Temperament and suitability for the role is more important right now than height. Chat to your regular instructor and see if you can ride on lots of different sizes to see where you feel most comfortable.