Some you can sex as they get older by their colors.
The only way I can sex them for sure is using their molt. As they get bigger is easier to spot. You have to look for little flaps between the book lungs for a female. The male won't have it.
Some people sex them by looking under the spider in that same spot and can tell,I can't. Using the molt is best way IMO
The spider doesn't always make it easy. Sometime they will ball up the molt or it gets ripped up. If I can get a fresh molt from her I should be able to tell with the next one.