I don't know, it doesn't sound like an English useage to me. A skinny girl could be round in cross section "Une fille cylindrique", whereas the plumper female could be more 3D & described as "Une fille spherique".
I think I detect a distinctly sexist bias in the French DL, which is not there in the Spanish.
A spherical girl in a vacuum :-) But, to be serious, this phrase seems meaningless in English, at least googling for it results into youtube videos of fighting women. The meaningful translation would be "plump woman", or as we would say in Russian, "пышка".
Is this a synonym to C'est une fille grosse? Or is there a difference in how french people perceive these expressions?