Thank you all for your advice and comments... Yep I use a tiny cat collar. It used to have a bell on it, but that really drives Nina insane! I will try the "good things happen when she wears a collar" tip (without the bell). And I think she's just about big enough for her harness now... before even the smallest setting would slip off! Now my baby is 16 weeks and 3.5 pounds, yay! She's so friendly and thanks you all too!
PS, anyone need a small purple and pink handpainted bell?