My 90 year old mother is heating me out of house and home!

Oh, I hear you. There's no way I can tolerate high temps like that. Your comfort matters and you have to take care of you too!

There are electrically heated throw blankets now (smaller than a twin bed blanket) that might solve the problem or just buy a twin heating blanket. Any tic of a higher electric bill from the electric blanket will be more than paid for by a lower heating bill.

The problem between hot people and cold people is eternal, the best you can do is try to reach a reasonable compromise with the thermostat. The statement that cold people can always add layers isn't always true, when the internal engine is running too slowly they can be under a mountain of quilts and still suffer with icy extremities (yup, I'm a cold person and I have struggled to warm my hands and feet, I shudder to think what it will be like when I am old and less active). Do what you can to get your mother off the couch every hour or so, even if it is just a trip to the bathroom or coming to the kitchen for a snack or to help with a little chore. Encourage her to sit out in the sun, nature's radiant heater, my mom loves it outside even when I need to cover her with a blanket..

Oh gosh, I hear you. I am in menopause now, too! I think. (I'll be 50 this year. I haven't had a period since August.  So yeah, I think this is it.) My mom has always been too cold (except in her own menopause years), but it's 20x worse now. She is so thin and frail, but refuses to eat properly or move around, so that doesn't help either.  Plus they give her blood thinners when she does dialysis.

Polar fleece long johns are a life saver here. Fuzzy socks. Mom has an electric fireplace where you can have the "flames" on with no heat, so I do that as a psychological trick. Lots of fuzzy blankets and sweaters. I keep her well-supplied with cups of hot tea.

Often I remind mom that I'm in menopause now.  Then she remembers her own menopause and has more empathy. (She used to run out in the snow in her nightie!)

I wear athletic shorts (with mesh inserts) and a spaghetti strap tank top, and keep my hair UP, whenever I'm at home - I did that all winter. I kept my bedroom window open all winter. I keep a 12" fan pointed at me constantly. I closed off the heat vent in my room. I drink a ton of water. I keep a spray bottle nearby and mist my skin as needed. Sometimes I walk straight into the shower - not even to wash, just to cool down.  (It helps a lot.)  I just got my hair cut shorter and thinned out in layers, just as a way to stay cooler now that it's warming up.

I don't know yet what summer is going to be like.  I'll be darned if I'm going to live in this desert climate in summer (in menopause!) without the AC running!

The thing is, the cold person can always add layers, but there's only so far you can strip down when you're overheated. Even being naked wouldn't help some days!

On Amazon, you can find heated jackets that use batteries to warm up. People usually wear these for skiing or being somewhere really cold. They are not cheap though. Here is a link to one.

amazon.com/Bosch-PSJ120M-102-12-volt-Lithium-Ion-Battery/dp/B00MXZI700/ref=cm_cr_arp_d_product_top?ie=UTF8

Thank you, all, for your replies and suggestions. There are supposed to be OT and PT referrals currently in processing. I hope to hear back from those programs soon. I'll check out sit and be fit, as well. Couldn't hurt me to do a few extra stretches, either. Life is, at present, more jack-in-the-box style, than a Yoga class!

Thermal underwear helped my Mom. And make sure the parent has their shirt or whatever they are wearing tucked into their pants, that can make quite a difference.

Well hopefully you will find the temp where you can coexist.
I would dress your mom in thin layers. Cuddle duds or 32 degrees are both good brands that are helpful in keeping a person warmer. A lightweight down comforter can line her chair and then wrap around her to keep her cozy. An artificial candle might help relax her without putting out heat.
Of course poor circulation, malfunctioning thyroid and adrenals, poor diet, lack of exercise, insufficient sleep all play a part in body temp. Some of your mom’s meds might be affecting her body temp.
As you say it is warmer outside now, can you make her a nice place to sit outdoors to soak up some rays?
It’s a real thing that some people are too cold so try to rule out all the medical ones. Keep a log on her diet. Pay attention to when she seems more comfortable. Add healthy fat to her diet like coconut oil, avocado, olive oil. Protein powders can be stirred in soups to boost her protein. Make sure she eats an egg with her breakfast. See if any of that helps to strengthen her. Of course she needs to move. Reward her for walking about the house. There are exercises she can do in her chair. Check out “Sit and be Fit” on PBS. Just gentle stretches can help. Ask her doctor to order PT or OT to get her going.
I know being overheated is as uncomfortable as being too cold so do what you can to address any issues and compromise with mom. You might want to clean early in the day, have fans in the area where you sit or work. Fans don’t actually cool the air, they just move it away from your body which makes you feel cooler. Sit a frozen bowl of water in front of the airflow to blow on you. A constant ice water drink is helpful. A room where you can cool off is also helpful. Try cooking in a slow cooker or microwave when possible. Wear loose cotton. Eat frozen grapes. Lol. I know it’s hard. Hugs.

Could she deal with an electric blanket? Sporting good stores sell heated sox! Sounds miserable for you. AND expensive to heat the house to that level!

I had that with my mom. I never found a good answer, but I didn't live with her, but when I'd go visit her, I'd be sweating buckets within a few minutes. In the summer, I'd call her and ask her what the temperature was. It would be 86 and she would be comfortable. We had a constant battle with me trying to get her to use her A/C. I was afraid I'd be accused of elder neglect if she died from heat stroke in her own apartment. I could NOT have lived with my mom. I'd have killed someone (my temper flares when I get hot). I hope others have some good solutions.

I'd get a little personal fan that I'd keep turned on and one of those wraps that go around your neck that you soak in cold water...beyond that, I've got nothing.

Anjolie, you said you're just venting, but maybe you need to vent even more (pun intended). My dad and I had the same problem when he was living with me -- he was always cold even though it was so hot I could barely breathe. Several clothing layers and blankets helped him quite a bit, so he must not have been as cold as your mom. She has a right to be warm, but it's hard to be a good caregiver while suffocating. You could try heating her blankets/jackets/bath towel/pillow in the clothes dryer or microwave. You might be tempted to try using a small space heater placed close to her, but I would advise against that due to the safety problem, unless you never leave the room or take a quick nap or a quick trip to the bathroom or kitchen.