I have a 13 year old no previouse medical problems
3 or 4 time a day she has been coughing like as if it's a furball but nothing comes out. Never had problems with furballs before. She is of siamese build if that helps.
Tha hacking can last for a few minutes at a time, what's going on?

Is she outside a lot? It could be an allergy or asthma or worms.
Try giving her some fish oil or a little olive oil and see if that helps
If you think it could be worms I would take her to the vet so they can determine what type of worm medicine would be best.

How long has this been going on? This could also be respiratory. Does her breathing seem labored or she's just doing a try hacking sort of thing? I had a cat that would do this for a while during the fall, which I think was due to dryness in the air, but it was never at this time of year. (Of course, I don't know where you're at.)

She may not have had previous problems that you know of. Cats hide things very well and we are then surprised when something is wrong. I would at least call a vet and see if they think you should bring her in. If you aren't doing it, at her age, and being Siamese, I would be getting lab work done on her a couple of times a year.