Are you at week 13 of growing, or week 13 of flowering?
If this is an ILGM strain, they rate it at 8 weeks of flowering under best-world conditions, so 10-11 weeks of flowering is realistic. If this strain came from someone else, you will need to check their website to see how long it should flower.
All that said… White Widow is known for producing little amber, and sometimes no amber at all, depending on which phenotype shows up. Keep an eye on your trichomes when it gets close to harvest time. If you get to the point of 100% cloudy trichomes and it stays that way for 1-2 weeks past the time you expect to be harvesting, just cut it down. Don’t wait. Even though you don’t see amber trichomes, it will still have the desired traits that White Widow is known for.
There are a few strains that do this, but White Widow is the most infamous for it.
Edit: I took another look at your photo. It looks like the majority of your pistils are brown, but they are still pretty straight. They will tend to curl in on themselves when they are getting closer to being ready. So, you might want to give it at least another week. Going by the pistils is just a general guide, though. There’s no substitute for getting a really close look at the trichomes.