I am another provider, but will be happy to help, if you don't mind. however, I will gladly decline if you prefer to have Mrs. Sandman answer.
I hope that my response can be helpful to you. I am not completely aware of all of the details of the original question, but if we are going to analyze symbolism in the dream we can discuss the meaning of the cat and the light switch individually: To see a dead cat or hear a cat being killed implies that you are lacking autonomy and independence in some area of your life. To see light in your dream represents illumination, clarity, guidance, plain understanding, and insight. Light is being shed on a once cloudy situation or problem. You have found the truth to a situation or an answer to a problem. Also consider the color of the light for additional significance.To dream that you cannot turn on the light indicates a lack of insight and perspective on a situation. A further question that I would have would be if you are able to turn on the switch in the dream? Do you feel that you are unable to move forward because of the hurt and denial of your pain being recognized or validated. Remember not to base your personal worth on the opinion of others or allow the negative thinking patterns (such as rejection, abandonment, or loss) to control you.
The cat can be representing your relationship with your mother. People will often come In a form of animals in dreams such as loved pets. The cat also be representing your "senses" or gifting. Which allows you to see what is taking place spiritually. The light switch being turned on is you coming to an understanding and being able to see clearly of what is taking place in your life. With your mother speaking to you in the dream is showing how she is guiding you to what is really taking place with your ex. Your mother is still watching over you even though she has passed away.