Thanks guys. Looks like she missed the date cut off. She has to wait until next April to apply for citizenship.
They didn't have those residency cards when I was in the process... is this an independent category like ILR?
I have never heard of anything like this before. Can you ask her what it's called?
As far as I know, she should have received two 2.5-year FLR(M) visas. I have no clue what residency card she might have as I don't know of any visa that is only valid for one year at a time.
In other words can she stay if the marriage is dissolved?
Only if she already has ILR before the marriage breaks down.
If she is still on FLR(M) and her marriage is dissolved, her UK sponsor is obligated to report the dissolution to UKVI and her visa will be cancelled, meaning she'd need to return to the US and will not qualify for ILR or citizenship.
Alternatively, she could stay if she could qualify for a Tier 2 work visa, but that would restart the 5 years to ILR.
She says she's on a "marriage visa" now. By which I think she means "spousal visa".
There's no such thing as a marriage/spousal visa that is only valid for 1 year and has to be renewed.
A spousal visa is valid for 30 months and is then renewed for another 30 months, giving 5 years for ILR.