You just flipped to flowering right? Perhaps she hasn't gotten to have her flowering stretch yet? She may surprise you and explode over the next little while. Also some plants are bred to be short, indicas are usually shorter and bushy for instance. Its not the size that matters but the health of the plant, she may be the best plant you ever grow.
Personally i kinda feel like theres been so much cross breeding and mislabeling over the many years that most seeds are a little bit of a mystery. ✌️