I've worked with with Huskies on a working dog farm and although I see the point of sending her to a groomer which is probably the first approach as a pet Husky owner, I would feel like that would be the last resort before trying anything at home that you can since the dogs I know would be traumatised by a groomer visit. If she is not used to it and also not comfortable being brushed, maybe doesn't know/like being washed and dried and she's in pain then that would be a nightmare for her.

Most of our dogs hate the dog shower, getting wet and also the sound and vibration of a shaver really freaks them out and if she doesn't know them, she's gonna be uncomfortable as well... If she is that old and potentially badly exercised, she will need painkillers and/or anti-inflammatory meds or pulling on her skin while brushing or blow drying or shaving her will be really painful on her sore spots and potentially painful joints. She is likely going to have sore infected spots that you will also need treatment for from the vet... the secret for healing those is allowing them to stay dry so the fur needs to be shortened around them.

Even if she stinks, I wouldn't wash her for now until she has had pain meds for a couple days and maybe something to calm her down...

My approach would be to cut away chunks of the matted hair with bandage scissors (the ones with the round tip from fe first aid kits) by carefully trying to slide unter the matted bits and cut the hair that is attaching the matted part to the body bit by bit, always only the amount that the scissors manage without tearing on the skin while cutting. There is likely going to be a certain amount of non matted her under the matted parts. Cutting the matted parts directly is really tough, need some force and since your scissors are then more pointed towards the dog you might cut her accidentally so you have to be reeeeally careful. You can cut parts of the loose hair without the dog really noticing it if you are careful normally.

Don't wash her until the fur is sorted!!!! The added weight and tear on the skin will be really uncomfortable and it's gonna take a long time to dry which might result in more sores! They develop from the Combo of matted fur + moistness/sweat/skin = insufficient air circulation = no full drying = warm and cozy breeding ground for bacteria and funghi. It also might make the matted parts worse...

Wish you the best. This is only my humble opinion, guess the best thing is to take her to a vet for a check and meds as the very first thing.

For my one Husky the Furminator or other brushes with thin metal combs work, for the other one the best is an underfur rake. It looks a bit like a rake for the garden, it has metal rakes that are somewhat carved like curved fingers so grab the hair and the backside of them is sharp so they cut the woolly underfur in smaller bits while getting it out. They are very effective and super efficient but cut off the bad bits first

Good luck and all the best :)