Instead of an electric blanket, you might also consider a rice sack/rice sock (uncooked white rice in a cotton container of some kind, socks are classic, microwaved on high for 1.5-2 min) or a heating pad with an auto-off setting. When I was growing up, I slept on the unheated 3rd floor, and getting the bed warmed up with a rice sack was Key. I alternate between the rice and a heating pad these days. The heating pad is nice because I can lay on it if I'm feeling tense in my back or shoulders and it's multi purpose, the rice sack is nice because you can cuddle with it a bit better or put your feet on it and it's easy to kick away if you overheat. You can also carry it around with you easily, if that's a thing you ever need to do?
For the insulating part, I don't know how it compares cost-wise with the electric blanket or just buying a fleece blanket, but a few yards of polar fleece in a nice pattern you like is pretty cheap at the fabric store and requires literally no sewing. You might need to trim the edge they cut to make it nicely square, or cut in a fringe if you're feeling fancy, but it's an easy nice-looking blanket. I still use the one I got from a friend in high school! Also, with a non-electric blanket, you can wrap up in it like a really big shawl and move around a bit. Depending on how cold it gets, you might want/need two blankets? The Marshalls by me also have what look like very cozy fuzzy almost 'faux fur' looking blankets/throws. Some look to be fleece on one side, fuzzy on the other, so probably pretty warm? I don't know how warm they'd be, but they're probably less bulky than a comforter?
My mom gets really cold all the time, and in the winter she swears by her polar fleece pjs. She has a few pairs at this points in various cheerful patterns!