Huh. She must be on to something but this is not how I thought things worked. My understanding has been plants absorb carbon to make cellulose, but when the plants die the carbon gets returned to the earth.
That’s how we are releasing so much carbon to the atmospher: we mine for dead plants (coal and oil) and burn them.
The only way to keep the carbon in the plants is to grow massive trees that live a long time and then get buried.