Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you.
I am so sorry Mona is experiencing this. Coughing in cats is never normal. Unfortunately her signs are vague and could indicate one of many possible underlying causes ranging from heart worms to lungs worms to feline asthma to heart disease to fungal lung disease (depending on where you live) to pneumonia to fluid build-up in the lungs to cancer. That is a list of diverse issues, some easily treatable and some not as easily.
If she is also lethargy and not eating well then I must recommend you consider having her seen on emergency today. The sooner we start therapy (prescription therapy is probably the only way; I wish I had some excellent at-home recommendations but for coughing there is not much over-the-counter that will help and be safe in cats) there better her potential outcome. And, since some of the things I mentioned can be life-threatening (fluid build up or heart failure), this is why I recommend you not wait.
Now, if she is otherwise doing great - still grooming, eating/drinking normally, reasonably active - then you could monitor today but have her seen by her regular veterinarian tomorrow. But if she is having trouble breathing, a lot of cough/vomit and is not eating/drinking then I recommend you have her seen now.
I am at a point I need to know what questions you have. I hope that the information I provided has been helpful.
Please let me know if for any reason you need further clarification, have more questions, or were expecting a different type of answer.
My goal is to provide the best answer possible prior to you leaving a feedback rating.
If you received all the information you needed, then kindly submit a rating.