Post hibernation anorexia is a common problem with tortoises. They experience a glucose surge in their blood as they come out of hibernation that triggers them to eat. If the surge does not happen, or they are not feeling well when it happens, then they miss this trigger. However we can help get them eating by mimicing the trigger. Basically we need to get some food down them and usually we need to do this be either tubing liquid food directly into the stomach, or with very compliant tortoises, by syringe feeding. There are many different foods you can use, but I find the vetark critical care to be the most easily available. Our usual protocol is to bathe in warm water once or twice daily (the additional supplements you are using are probably a good idea but she won't voluntarily take in enough at this stage for them to replace assisted feeding). Then we tube them once daily with about 2-3% of bodyweight food. Keep her nice and warm as you have been and get outside when it is sensible to do so. We usually offer some of the things that are usually considered treats not staples- such as strawberries and banana. Dandelion does seem to work well as well. We also record the tortoise's bodyweight on a daiy basis - we expect to see them gain weight due purely to the fluids they take in, not lose it. Until they poo that is! We usually see a nice big poo as a precursor to them starting to eat.It can often take 10-14 days of this therapy to get them eating again. If it takes longer than this we suspect an underlying health issue, such as respiratory disease or egg binding. It may be worth taking her in for health check with a vet to see if there is any obvious disease. Egg binding is usually diagnosed with an ultrasound or an xray.
So basically you are doing the right things at the moment, but you need to add the assist feeding in. Some tortoises are really tricky to assist feed, and those are the ones we end up hospitalising to do for you, or in some cases to place a semi-permanent feeding tube into.
I hope this information is useful to you and please let me know if I can add any additional information.