Don't know anything about a 3-day cure... but I have also heard that Nystatin does not work very well (that's the one thing I haven't tried, for that reason). And FWIW, gentian violet damaged my nipples, causing cracks, bleeding and infections that eventually lead to my being completely unable to use my left breast. Don't get me wrong, the GV kicked the thrush out, but it also caused the worst pain in my life - worse than the actual yeast.
I'd suggest looking into kefir, as that truly helped me for a bit, but it's not vegan. (I have heard of something called water kefir, but I am not going to pretend to know what it is.
Rather than relate the whole agonizing, ongoing, endless story of my thrush battle, which started when my son was 4 weeks old and still periodically flares up (he's 14 months now), including a brief, emotionally-agonizing period wherein he was wet-nursed by my then-friend followed by having to supplement with bottles just a couple of weeks later (I don't recommend allowing a friend to wet-nurse), followed by losing the milk in the left side because of the damaged nipple... I will just tell you what I do now.
I do swab the inside of Lil'Man's mouth with GV if I see a thrush spot. Just once. Just him. NOT me. And directly AFTER he nurses so much of it is absorbed by the time he nurses again. Usually that clears him
right up. (Use only the 1% solution. I've never heard about a cancer link, but that stuff is so vile it wouldn't surprise me.)
For me, I break open a capsule of grapefruit seed extract, mix it thoroughly with about 2 ounces of water, then pour that over the nipple right after I nurse. Let it dry and rinse it off before nursing again. Then repeat right after nursing. If it hurts, I also may lather the nipple with cold, plain yogurt. (It feels better and it's beneficial as well.) Because of the h*ll I have gone through with this yeast, I hit it hard at the first sign of burning (which always seems to happen right before he cuts a tooth). It usually hits me before I see any spots in his mouth. But doing this, it actually helps, and I have tried EVERY.THING in the book. I've even spread Vusion anti-fungal cream (an Rx for athlete's foot) on my nipples - it doesn't wipe off very well, so I don't recommend that either - as well as sunbathed topless on someone else's porch because sunlight is supposed to kill the yeast. This method with the GSE and yogurt as well as one single GV swab to the baby has been the most effective thing I've used. Luckily, we only have to deal with it about every 6 weeks or so now, and it's not very intense. Like I said, it's when he's teething. Maybe there's a connection.
There's another thread on here somewhere about dealing with thrush, it's pages and pages long, so you can get a lot of different ideas about what to try. For me and Lil'Man, the expensive probiotics didn't even do a d#mn thing.
I do suggest that whatever you try, you start NOW. The sooner the better. This stuff gets it's hooks into you and it's desperately hard to get rid of sometimes.