It may be a bit of selective memory on her part and if an actual comparison was made, rather than relying on memory, it might be a different story. Chemical mordants were developed exactly because naturally fixed pigments fade significantly:)
However, lime green and turquoise, perfectly achievable using natural dyes so fill yer boots
I have many photos of tests on cloth and wool using natural dyes and fixatives and it was possible to produce a veritable rainbow of colours (don't believe the rubbish about there being no purple unless you mugged a shellfish).
A while back I made this, rather scrappy, guide for my own use. I used colour swatches from dyed wool and made the colours wargames friendly.(There is no significance to size of swatches, it just very badly presented )