You are mixing two separate issues together. Your comment is kinda like saying humans can't see heat. I find that hard to believe since they clearly don't like being set on fire.
Lets say you have two people that you don't love that want to go for a ride in your new car. You only have room for one though. Do you choose the person who is wearing deodorant or the one who is not wearing deodorant. A snake could recognize (a talent that is unrelated to love) the person who has cared for it for years vs the new person. Its going to be calmer with its keeper than the new person. All of this is unrelated to the ability to love.