That article though states she was the first woman to be executed since 1953..... what about Aileen Wuernos who was executed in 2002, they seem to have forgotten about her!
I think they mean the first federal execution of a woman in the US. Most crimes in the US fall under state jurisdiction, including most murders, and are prosecuted as such. And states differ on whether their laws support the death penalty. About 30 times as much crime falls under state laws as federal.
Federal crimes include crimes that take place on US Federal property and crimes that have a national or federal interest.
Personally, I think this case demonstrates the failure of society, and US systems specifically, in every way. US systems failed to identify and safeguard Montgomery, they failed to offer her mental health support before her crime, and they failed in their ability to have a justice system that is capable of rehabilitation and the prevention of recidivism, so in its failure all it can think to do is kill people. I oppose the death penalty in all cases, although I admit there are some people I wouldn't be first in line to go to bat for, but I think this is an egregious case and an enormous abuse of Trump's power. It is proven that the US justice system and the death penalty in particular is hugely racially biased, and that it has executed people who in all likelihood are completely innocent. That is monstrous.