I think it might be the one, we've really struggled with a girls name, I love DDs name so much that finding another one I love equally is really hard!
cheese greta could be funny nickname if she's as keen on cheese as her big sister
and no we're not the Von Trapps, though Martha was originally going to be Marta, I do like a good germanic sounding name!
I thought of Greta because I met a 5 year old called Greta the other day who was dressed as a cat!