I strongly agree with Naomi's suggestion of putting her back in cloth diapers. She can feel she's wet while not leaving stains/puddles on furniture. It's not fun for her to be wet.
I see a lot of discussion regarding power struggles. In my experience, power struggles can be minimized if we let this be the child's learning experience and don't internalize it for ourselves. This means not punishing and being very matter-of-fact about cleanup. At my preschool--as well as at home with my 3 y.o. son-- I treat accidents as such: if it's pee, they are asked to change their clothes and given a plastic bag to put them in. (They sometimes need help getting the bag to stay open, so I do assist in holding it for them to put their pee clothes in.) I ask the child to change themselves independently. For soiled pants, I help, partially because I believe it is demeaning and upsetting to some children to have to handle feces and also because this usually requires more cleanup. I do, however, have the child help with other things like holding doors open, taking the plastic bag of cleanup rags to the laundry, etc. If there's a puddle on the floor, children can help to get a bucket and mop or sponges, and when the mess is cleaned up, they are asked to use a dry rag to dry the wet areas on the floor, to ensure it isn't slippery. (I usually just ask them to dry the floor so no one slips, to "keep their friend/family safe".)
I am also of the belief, after years of working with little ones, that children need to be TOLD to go use the toilet once every 2.5 hours or so, not asked. "Do you need to use the potty?" leads to a lot of reasons to say no: playing, exerting autonomy, unfamiliarity with one's own body's cues. Instead, I tell the kids that they need to use the toilet. (This is depending on their degree of needing help, of course.) Noncompliance? "I need you to sit in this chair until you are ready to sit on the potty." and follow through. And I never have them sit for more than 4-5 minutes. You can use a timer and walk away, leaving the child with a book if need be. Kids sometimes like company, and sometimes want privacy; the point of this is to help them relax,which facilitates elimination. Chances are, if they sit on the potty and nothing comes out, but then go play and pee/poop their pants, they are having some trouble relaxing on the potty or are feeling pressure to "produce", which is an indicator that some sort of power struggle is in fact going on.
We don't want to "Conquer" our children, but to give them the emotional room to work through this challenge--even if it is their own stubbornness--on their own. The ultimate consequence IS the wet/soiled pants and their own frustration with themselves. If we get involved emotionally, we often get in the way of them figuring this out for themselves and the results being more long-lasting.
I've found that for many kids, both stickers/rewards AND punishments prolong the process and increase the cause for power struggles. ("I peed. I want a sticker." mom:"No, I can't see the pee." etc.) The pull-ups are, in my opinion, one of the most parent/child enabling devices in delaying success on the toilet as well.
I do understand your concern around preschool/classes, and what I have to say is this: there are programs out there who take kids who are in the process of toilet learning. I certainly do. Some larger centers have different state guidelines around this, but smaller programs may not, so look around. A toilet-learning child will likely need the support a smaller program can offer.
Lastly, and this is important, if you can emotionally extract yourself from the process and let this be her lesson to learn, just acknowledging when she makes it to the toilet on time and not giving much attention to wet diapers (and they really do need to be diapers-- my son got a choice of cloth diapers or training underpants, both choices help the child understand the connection of wetting and being wet and uncomfortable). If you are the only one motivated-- you will be doing all the work. She's going to have to figure out on her own what her internal motivation is. Trust me on this.:)
Best wishes!