You must have quoted me as I was fixing the typo just after my initial post (had question on where your number was coming from and initially typed in your total, which is the number I had in my head). The total for just a spouse is $1040 : $75 app fee, $475 principal applicant and $490 for RPRF. For dependents you don't need to pay RPRF but you do need to pay the application fees based on age. It's $150 for each dependent applicant under 22 so if her 3 kids are under 22 the $1490 now makes sense.
If you are paying online then you need to have CPC-M manually enter payment into your file (the Outland Processing centers don't have that capability). Email CPC-M using the link I gave you earlier, attach the fee payment confirmation, and hope they confirm once it's done. Then you can reach out to Mexico and alert them that it's done. Otherwise, you need to wait for it to make it through the system automatically. This path takes longer than paying at the Embassy because if you pay with a Mexican bank check in local currency, the Embassy can input the payment and immediately see the update.
So, at this point, the driver for your wait will be processing time for the payment. Have her use the time for her B4 and for you to finish up those home improvement and closet clearing out activities.