A shorthair with matts is unusual. Especially since she hasn't done
this for 5 years. Perhaps a visit with your vet is in order. There has
to be a reason why she is starting to do this. and maybe the vet can
provide you with the appropriate help in getting rid of the matts.
Perhaps a change in food can help. I know Nutro puts out a food
formulated for a healthy coat.

My cats never get matted and I seldom brush them. The one longhaired
cat won't let me. But once in awhile I get my son to hold the cat and
then i use a comb with rotating teeth that goes through the hair very
well. It is recommended for matts. I found it at PetSmart several
years ago.

CATherine