I don't know about the show heights, but as to just general "being able to ride" heights - it really depends more on the build of the horse than the height. I had to laugh at you saying 13.2 would be too short for someone 5'2. I'm 5'8 and rode a 13.3 hand Haflinger for years. But he was WIDE which made a huge difference.
I laughed at that a bit too... in high school my 5'10, very light, and super leggy friend rode her 13.2hh mare until she was about 16 or so. She looked a bit funny on her and ultimately moved up to a 17hh horse, so I do understand the desire for something that fits a little better... just find it funny.
At your weight you don't really need to worry about the "Can the pony carry you?" argument, but it does become an issue of how long you will look well matched for the horse. When I was 15 years old, 5'3, and about 105 pounds I was looking at horses 14.2-16hh (I wasn't fond of larger horses) under the assumption that I may grow a couple more inches and wanting something my trainer could easily ride. I didn't grow anymore, and my 15hh horse fits me perfectly. You don't want something that will be giant for you, but you don't want something that you'll be too tall for if you have a growth spurt this summer!
Given that your 13.2hh pony is too short, and you are only 12 and are likely to shoot up a few more inches over the next few years I would look for something 14.2hh or up, unless it has a wider girth to take up your leg. My leg falls higher on my 15hh QH than on the 15.3hh TB I rode last summer because the TB was so much more narrow. It really does make a difference!
If you are willing and ok to lease out or find a decent home for this horse once you outgrow it in height or ability then I wouldn't look at anything larger than about 16hh. You will likely look small on it. Of course, large horses seem to be "in style" nowadays, with no one batting an eye at a giant horse with a tiny rider, and tall riders on short horses getting funny looks. Whatever works for you.
Most importantly, sit on the horse! We can give you all the height advice in the world, but unless you actually sit on the horse and see where your leg falls then you won't know. I would personally look in the 14.2-16hh range, and have someone take photos of you while riding so you and your trainer can see how you look.