If she responds to the positive stuff from nursery I would honestly give this a go: https://www.coursera.org/learn/everyday-parenting/home/welcome
It might help change the dynamic. Some of it feels overly weird and forced but they're all just things you can try and see if it helps.
I have also found the How To Talk books really helpful and the books by Dan Siegel and Tina Payne Bryson are also absolutely brilliant. Lastly there is an absolute hidden gem called "When Your Kids Push Your Buttons" which is only 99p on Kindle and is one of the best parenting books ever.
It's a really challenging age. I totally struggled especially with my eldest - it has been a bit easier with my younger two (they still hit challenging stages though!)
BTW, you say until recently she was a delight - when she was 2, how did you get her to do stuff that needed to be done? I do think I fell into a trap, and now I've seen it in hindsight I can see others falling into this too, I loved all of the gentle, co-operative, feelings, lovey, fun, positive, playful stuff when DC1 was tiny and thought I really had the toddler thing cracked and I was great at setting boundaries but in reality, the fact is that two year olds are really easy to persuade, trick, distract, and manipulate into thinking that something is their idea and every time I thought I was holding a boundary, I was actually just doing this, and this isn't boundary holding - it's sort of bending and stretching around a boundary so that you never have to actually show it to them because if they become aware of the boundary, they get upset, and I really found it difficult when he was upset if I felt like I didn't absolutely have to hold that rule (e.g. it wasn't difficult to physically move him away from the interesting, glowy hot cooker, and I didn't feel bad about doing this - but I would definitely tell him the biscuits were all gone, rather than just saying no, because it was easier than enduring a tantrum.)
So I had an absolutely wonderful time at two, never a "terrible" moment at all, but then three came along, and three is really not so easily persuaded, they have much longer memories and don't forget or get distracted as easily. Three knows what they want and they have much more stamina and stubbornness than Two. Three is contrary and they will pick a side which is opposite to you and run with it even if they can clearly see that their side is wrong, just for the experience of seeing what happens. Three is fierce and you need some boundary holding skills for sure at three.
Some people HATE two and find it an utter nightmare, because they are trying to hold boundaries in a verbal/traditional way and two year olds don't understand this a lot of the time so it leads to a lot of frustration and tantrums, but by three they are pretty much getting there and/or there is enough repetition that they are beginning to predict the basic expectations, too.
OTOH if you get to three and this is the first time that you actually have to hold boundaries, it's really hard. Hard because I wasn't practised at it but also hard because my 3yo didn't have the experience of the repetition that most 3yos have experienced, and hard because I struggled so much every time I felt I was upsetting him which then undermined my own authority. I didn't feel confident because I could no longer persuade him to like and agree with all of my choices. I would have had a better time if I had known that it was totally normal and fine for him not to like what I had decided and that it was not at all cruel for me to make decisions, nor was it my job to get him to agree with me! It was just my job to make sure things happen and that I communicated clearly in a way he would understand, and provide sufficient structure and so on that things are predictable and he knew what the expectation was, rather than thinking I was modelling flexibility by bending and flexing all the time.