how tight was the collar? it should only allow you to fit one of your fingers in there next to the dog's neck, otherwise i think it's a little too loose.
milu wears a cat collar, honestly, i don't even know if she is strong enough to "break away" if she needed to. so i am not sure how much safer it is from a regular dog collar?
do other ppl have experience with their dog being able to take off the cat collar?
my advice would be to make sure it's tight enough. that way the dog won't get her mouth caught. but make sure you check every week to see if it is still fitting comfortably. too tight is bad and dangerous.