Cat is chewing off fur

We've noticed cat hair in clumps recently. This isn't normal behavior at all. We got her groomed two weeks ago and gave her a Lion cut cause she sheds so much. We haven't changed her food. We have had her for 6 months and she is only a indoor cat with no other pets in the home. No fleas. What could this be?

Are you positive there are no fleas? Fleas can happen both in a short coat and in indoor kitties who have never been outside (and it's possible if she went to the vet for the haircut she picked some up while there). Often chewing at the base of the tail like that is flea related (obviously not always but often).

Has anything else in her environment changed at all? New washing powder? Cleaners? New plants?

What is she eating? Often times over grooming/fur loss is caused by a food allergy. They can come on suddenly for no reason at all, which is why it's encouraged to feed a protein rotation diet.