Cat not grooming herself?

My cat is 7 years old and has medium length hair. she likes to roll around in the sun, but gets the dirt all over her. I have noticed lately that she doesn't seem to be cleaning it off. Everytime I pet her my hand is covered with dust and dirt. I have had to giv her baths before, but I don't want to keep doing that. she is also in the prime sheding season. She sheds year around, but it is really bad right now. I was just wondering why she would be so dirty if cats are supposed to clean themselves. I have to use hairball control treats because she has had problems with them before. She has really dense fur and only tolerates a brush. She likes being pet, but then I'm covered in hair and dirt. Is there anyway to minimize the shedding and keep clean fur?
P.S. she leaves dirt marks in her favorite places from sleeping there so often.

I don't know the answer to this, but mine does the same thing. He loves to roll in dirt, now he does groom himself but rather slowly. He will walk around with the dirt for a long time. I am surprised too, I have had 6 cats in my life and never had any of them do this. But it's ok, I am used to it now.

Work on brushing her every day. If you really want to use a comb, let her get used to it and be careful to not pull. A medium or long haired cat cannot be expected to groom all that constantly, even if she tries! Imagine if you were a kid with long hair and went out to play in the mud, and then your mother expected you to make your hair clean and spotless with just your fingers. Uh, no, mom Humans who take in cats should realize that they're making a lifetime commitment of care including weekly brushing in the case of shorthairs, and up to daily in cats with longer coats.

Once you get in the habit of brushing her head to toe every day, she shouldn't get hairballs any more. These are very unpleasant for the cat and a properly cared for cat won't have any problems with them. I don't think ingesting all that dirt in an effort to clean it off is very healthy, either.

If you don't have a cat-proof enclosure, try building one where the grass is thicker, for example. It might cut down on the amount you have to brush off. And cats outdoors should be confined and supervised, anyway.

If it's really bad right now, ie large dirty mats, ask a professional groomer for help. Easy daily maintenance should be enough after that.