ANSWER - It is perfectly natural to be able to see spirits. It is particularly common at a young age before preconceptions of the world are formed. Some individuals are more in tune with spirits than others. I know witches who incorporate working with spirits into their craft and others who wouldn’t recognise a spirit if it did a jig on their head. Witchcraft and an ability to perceive the departed are too often seen as being dependent on one another when in fact the following of a craft path can be entirely free of spirit work and any individual can have an encounter with the departed without needing to be a practising witch.
I like your rather pragmatic approach to the spirits you see. Certainly it does not have to be anything dark or frightening. They just are in the same sense that anything else just is (and you are right to stop them scaring your cats, lol). I would continue to view your ability with this very common sense approach. There is nothing wrong with you, nothing abnormal or worrying. You may find this gift brings an element of inconvenience at times but there is no reason why it should have any negative impact on your life.
In terms of your cousin telling your mother you are a witch, I think you need to open up a bit more dialogue on this. Give her a ring and ask her what she meant! I’m not a big believer in the idea that a person is born a witch, though I do acknowledge there are some hereditary craft traits, so I think it more likely she is being sensitive to the changes in you since you started practising. Working with magic does change us and it is certainly possible another witch has picked up on this. But like I say give her a ring. Direct communication is often the straightest path to clarity.