It sounds like your dog has already beeen treated by a vet - not sure what for tho... What kind of surgery are you and your dad talking about? Usually a biopsy will be done on lumps that could be suspicious b/4 considering surgery.
If you feel she is sick and needs vet care you father could call your vet and see what he suggests. Not eating is not good. Please call or take her to a vet. I hope your dog gets to feeling better soon.