My wife is 63 and recently retired from OPERS. She took a plop to reduce her monthly benefit to help SSI because of the WEP provision. Currently she is receiving 1950 month and if she starts collecting SSI at 64 it would be $270. It goes up $21+ a month for every year she waits which does not amount to enough to offset waiting. I am 57still working and am self employed and have not paid a substantial amount into SSI. Not sure how her spousal benefit from me would affect her future SSI. The question being should she start collecting now or wait based on her portion of my SSI.
If your wife is receiving $1950 per month from a pension based on government work not covered by Social Security, it's unlikely that she'll ever receive a spousal benefit on your record. This is due to the Government Pension Offset (GPO) provision, which reduces Social Security spousal or widow's benefits by 2/3rds of the amount of their non-covered pension (https://www.ssa.gov/pubs/EN-05-10007.pdf).
So, your wife will need to make her decision on when to start her benefits with the understanding that she likely won't receive any other benefits for at least as long as both of you are living. You're correct that due to the Windfall Elimination Provision (https://www.ssa.gov/pubs/EN-05-10045.pdf), there probably isn't that much of a difference dollar-wise between your wife's current benefit rate and what it would be a year from now, but it will get higher the longer she waits to apply until age 70. WEP does not preclude delayed retirement credits, so she can receive an 8% increase in her benefit rate for each year she delays taking benefits between full retirement age and age 70.
Bottom line, deciding when to start benefits is always a personal decision, but you may want to run the maximization software available on this website in order to be sure that both you and your wife make an educated decision on when to file.