Yep. I originally said 25 years but then I saw your profile so I amended it to 35 years as Mexicans have a much longer wait.
There is only a small amount of sibling visas available each year, so there's a huge line ahead of you for them. The Visa Bulletin will be what your wife needs to look at to give her an idea, as you can see in category F4 (siblings of USC's), those who applied in 2001 are only now eligible to get visas. Add on the time for your wife to become a USC, and additional time as the line gets longer each year due to more and more people applying, and I'd say at least 35 years personally. https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2024/visa-bulletin-for-july-2024.html