So I've been bathing daily, and wrapping in clean micropore tape. Today I sterilised a blade and re-opened the scab, and squeezed out some blood and a tiny bit of pus came out but nothing like I'd have expected. It clearly causes pain, although she is being very good about it and seems to enjoy her feet being in the hot water - she proper settles down into it. The lump is now soft, rather than rock hard, which I think is a good sign. She is still eating and drinking and is standing up and seems to be weight-bearing on that foot now, although can't walk far on it. I feel so sorry for her! I will just carry on until she gets either better or worse ... !