Hi I'm Rosie one of the vets and I'd like to try and help you and Molly. I'm sorry that she is attacking her fur like this. The tricky thing with skin conditions is that there are quite a few things that can cause this type of behaviour, and they all tend to look quite similar on the skin. However, there are a few things that it could be.
If it is seasonal - i.e. happens at the same time every year - then it is highly likely that there is an allergic component. The allergy makes them itch, and they pull their fur out in response. This typically happens in response to certain blossoms (tree/grass etc) that only appear once a year. Even if she is an indoor cat this can still happen, as sometimes these patients can be very sensitive. If it is an allergy then simply bathing her fur once a day (if she will let you) can remove some of the things she is allergic to. You could do this by rubbing a damp washcloth over her - I don't think she would tolerate a full bath! Antihistamines can also help - if you can get any then most cats do well with piriton, and I would give her half a 4mg tablet twice daily. You should find this over the counter at your pharmacy. Sometimes it can make them excessively sleepy, and if she is one of those patients then just halve the dose. As it happens once a year I think this is the most likely explanation.
However I would double check that your flea control is up-to-date. Typically fleas make cats itchy around the tail and extending up to the ribcage on their backs. They end up with a bald area with short spiky hair where they have been pulling it out. There is a really simple test you can do for fleas at home (as really itchy patients eat the fleas themselves so you hardly ever see any). Damp a small piece of white toilet paper and rub it over her fur. If the paper turns red, this is indicative of flea poo, and you will need to treat her for fleas. If necessary, you should be able to get some treatment over the counter at your vets, or sometimes in a petstore.
I hope I've helped - if you have any questions from this or need clarification then just get back to me. Otherwise, if you have found this useful, please leave a positive rating. Thank you, ***** ***** luck, Rosie.