Urgent! Need advice! Neurologal Issue

[Yuki]

So I have a elderly silkie currently 7 and half years old, I got her from a inbreeding suitation most were roosters and very few hens were left and were free rangers. The owners kept hatching eggs without adding new blood into the mix. So the silkie I had gotten when she was 1 and half yr old. She has neurologal Issue with a head tick took her to the vet he said she was find and at the time it would happen to fast I couldn't get video of it. But now she has gotten sick recently around time with it was -7F one night her health started to drop along side of my 9 yr old hen. I had lost one of her siblings, could be daughter or aunt of the younger one who passed. So 7 and half yr old hen and the 9 yr old are out under a heat lamp and separated from rest of flock not both at the same time 9 yr old got put in few weeks after the 7 and half yr old. So recently she has gone down further with starting of lameness but she will moves around a bit but her head keeps bobbing more aggressively. She's barely eating and with her old age she's skinny and can't gain weight for anything. Been putting her favorite treats in front of her she's not eating them. Went out a bit ago to find her head swaying side to side constantly she's a bit wobbly before I had thought she was going blind as she could peck at the food right but to find out with her episodes of her nero issues sparking up 100x worse than it was. She was really chatty with me as well tonight but I feel no food in her crop but she's swaying side to side with her head has me worried she has close access to food and water I don't know it's me coming late at night and or early morning when they r supposed to be sleeping that she's not fully awake causing her episodes or the temperature change. She's very clumsy right now and has hard time walking over obstacles like food and water bowl but very close access too. To the drastic changes on this I need advice. I've been dealing with chickens with medical issues for 14yrs and I'm not good with nerological issues. She doesn't have Mareks if she did survive it she would be a carrier and would be spread to my flock by now killing them off.

What's being done for the hen, electrolyte and vitamin and mineral water, extra protein feed, mealworm, black oil sunflower seeds, mix of mealworm and pumpkin seed mix treat along with being under heat lamp and deep bedding of shavings. A bit earlier she was alert besides the head bobbing and swaying that was constant. She did react when I called her name and has pet her along with me picking her up. She refused to eat her favorite treats of salmon catfood, raspberries, pumpkin seed with mix, blackberries and I haven't seen her eat the berry sutte? She's clearly eating enough to get by and not pass away on me. She was very alert asking with reacting to me moving my hand closer to her face and no signs of cataracts or any of the foggy white in her eyes.

I'm terrified to take her out from under the heat lamp with the drastic temperature change to take her to the vet would send her into shock and kill her. I've already lost 3 in the last yr old age age range was 6yrs to age 7 and half yrs. I really don't wanna give up hope yet on her. I just don't know what else to do as she's a pet I want to make her comfortable as possible but I want to try and make her recover even if it means get needing to be smaller space for rest of her life

 

[Yuki]

Forgot to add she's never had an full blown seizures

 

[Yuki]

Those 2b that were related to her one was perfectly healthy and the other younger one was short and chunky with breathing issues when it was cold and winter