Should I get the horse :/ !!!!?

I suggest you stay with your riding school. I've leased/owned horses that weren't a good fit for me(size/level wise), and even though they're great animals to pet and love, if the horse is wrong for you, you won't have as much fun as you COULD have on another horse. If this pony is too small for you, then I suggest you don't lease her. Unless her movement is perfect, and you don't have any difficulties with her, stick to your riding school. You should save your money to get a horse that fits your size, so you can feel more comfortable on them, and so they feel more comfortable with you.