I agree with elbrant....If you want growling behavior to cease, you must correct it in BOTH dogs. Basenji are very good at learning from their humans AND from other dogs. I had a purebred Basenji that taught herself to make a reasonable imitation of a bark-she learned from the other dogs at the dog park!!!! I would make a really concerted effort with the chihua-once she starts to curtail HER growling, I have a feeling you will see less from your Basenji, too.
My Goldie was half basenji, and her tail only curled a little, and she had LOTS more fur than a Basenji, but she was Basenji through and through in her actions, her attitude, and her lack of barking. She could bark, but did much more Baroo type vocalizing. Sweet Goldie got us started on a life of pure bred curly tailed clowns!!!! Your Ely is just beautiful. If you do decide to do her DNA, let us know. Whatever you decide, you are going to have a lifetime of love and laughs!!!!!