I'm sorry, I don't know if I'm miss reading your post, but is your question on how to know if she's building or if she's gravid?

Signs of building can be bowl wrapping, staying on the cool side, laying inverted, etc. I also notice mine look really big and sometimes lumpy when they are building. If she's gravid she will typically stay on the hot side pretty much non stop curled up. They can also lay inverted when they are really close to laying, I believe to adjust the eggs.