My Widowed mother receives a non covered pension from her teaching career of $3500/month. Her pension has an annual inflation adjustment. Her husband, who she had been married to for 50 years, died in 2007. My mother was well past FRA at that time. At the time of his death, he was receiving a SS benefit of $2000/month. I assume my mother’s SS widow benefit is subject to the GPO. Currently, she receives no widow’s benefit, as 2/3rd’s of her pension completely offsets the $2000 benefit she would otherwise receive. However, if you apply a COLA to his benefit over the 13 years since he passed, perhaps her widow’s benefit would be greater than $0, even after the GPO! Is this how it works?
Yes, that's basically how the Government Pension Offset (GPO) provision works. Your mother's current widow's benefit rate would include any Social Security cost of living increases that occurred since her husband's death. But, unless she meets an exception to GPO (https://www.ssa.gov/pubs/EN-05-10007.pdf) her widow's benefits would be offset by 2/3rds of the current amount of her teacher's pension.
If your mother hasn't yet applied for widow's benefits she may want to consider doing so. The worst that could happen is she'd be told that her benefit rate is zero due to GPO. Or, if she's already applied for widow's benefits and her benefits are suspended due to a full GPO offset, she may want to contact Social Security to update them on her current teacher's pension amount and check to see if a full offset still applies.