Hi everyone

May I seek your advice please.. I have a 6 year old domestic mid/ long haired ginger female, adopted as a stray from when she was just a couple months old. She's been fully indoor ever since, and only exposure to the outdoors would be during her visits to the vet - or whenever we have visitors at home (she's easily scared and thus usually hides in my room)

She had flea infection once, a couple years back - which was cured with Advantage spot on + diatomaceous earth powder.
She probably caught fleas through me, as I used to take care of a couple of other strays within the area too.. I've since taken care of the flea issue and she's been flea free since.

She broke her leg once probably 3 years ago, whilst running around at home. Brought her to the vet, all good and she was up and running in a couple weeks. Though, she picked up ringworm - I would assume she caught this at the vet itself, likely through the clippers used to trim her fur. I showered her frequently with Malaseb, and used medication provided by the vet to rid of Ringworm and she's been good since.

In early October 2019 - she had her regular scheduled annual vaccination. To which we made the dreaded trip to the vet. Vet determined she was all in good health, provided vaccination and we brought her home. HOWEVER, this is where things started to get really...itchy

A couple days after the vet visit, she started to itchy and was offen seen scratching using her hind legs, excessive licking of the bottom half of her body and nibbling (biting) herself. Mid October, I applied Advantage again, and started to shower her with Malaseb as well as powering her with DE just to be sure it wasn't another infection. Fast forward to mid-December, I started to notice bald patches at her hind regions, legs, and smaller bald patches on her ears. There were wounds (or scaly skin) due to her excessively licking and biting herself but did not look like ringworm. Seeing no improvement, I brought her back to the vet and they confirmed it wasn't ringworm but instead fur mites (mange?). They also reconfirmed by gut assumption that she could have picked this up at the vet during her last visit (which is why I dread bringing her to the vet). She was prescribed Frontline & Broadline spot on (seems Advantage doesn't work for mites). I've applied the necessary spot on, whilst dusting her bald areas with DE since.. but as of today, I do not yet see any improvement.

She still itches, and lately I've noticed that she has been increasingly licking and biting her ankles - more scaly skin and bald patches. I've applied another dose of Frontline a couple of days back and still dust her scaly skin regions with DE but nothing seems to be working.

What should I do? I've ordered Machiko shampoo and some sulfur bar soap online that should be arriving next week. Should I stop DE? Because all she seems to do is lick the power off the dusted areas.

I'll probably give her a shower with the sulfur soap next week and apply Broadline spot on a couple days later. In the meantime, your advise is much appreciated.

Thank you.

Edit: located in Selayang/ Kepong btw - so if you have recommended vets that could help with this issue, please suggest as well.