Well, I'm not an expert in this, but Kelleen stated that she "knows" that
spayed female dogs will not allow males to mount them.  Guess what, Kelleen?
I've had two spayed females that did allow this.  Also two mares and a
gelding that let other horses mount them.  So, I'd venture to guess that in
ferrets as well as these other species, enough individual variation in
behavior exists that behavior alone is not a reliable indicator.  Has a vet
seen your girl?  Can he/she see a scar or palpate a uterus?  These would be
more reliable methods I think.
 
Hillary
[Posted in FML issue 1355]