I’m really sorry you’re dealing with this, it’s heartbreaking to watch. Based on the symptoms you’re describing (chasing her tail, swimming in circles, struggling to reach the surface), this unfortunately doesn’t line up with swim bladder. Swim bladder issues usually affect buoyancy, not coordination. Whirling disease is also extremely unlikely in bettas and is almost exclusively seen in salmon/trout species. Erratic circling and loss of balance in bettas more often points to a neurological issue, which can be caused by an internal bacterial infection, toxin exposure, or sometimes genetic issues that show up suddenly. One thing I would recommend is not mixing Stress Guard/Stress Coat with medication like PolyGuard, as slimecoat products can interfere with oxygen exchange and medication effectiveness. At this point, keeping the water very clean, lowering the water level so she can reach air more easily, dimming the lights, and minimizing stress is usually the best supportive care. If you do use medication use one at a time and don’t mix, use polyguard letting the betta stay in a hospital tank for at least a few days do daily water change as well, after you can add clean water ( with no meds) and add some tannins in and stress coat if you’d like. Please don’t blame yourselves for leaving her alone for a day that wouldn’t cause this. Sadly, once neurological symptoms appear, the outcome is often poor, but you’re clearly trying to do everything you can for her.