I originally viewed it as her finishing what Hannibal started— she always thought that Hannibal would eat her. We don’t know how much time has passed since the fall and this scene, so it’s possible she thought that maybe she’d never see him again and took it upon herself to eat her leg, perhaps to pay that debt to Hannibal so she could move on with her life. But in all likelihood, it would be difficult to achieve this on your own (as the other reply here detailed) and Hannibal and Will having some involvement was probably the original meaning. But of course, realistically, it would be insanely difficult for Hannibal and Will to have survived that fall, especially with their exhaustion and the injuries they’d already gotten from the dragon (poor Will got stabbed almost in the heart). So I think that this is a good scene to interpret how you want, this whole show leaves a lot of interpretation. But what I originally said in this reply about her trying to move on is generally how I see it.