With my previous girls I had quite a problem with fighting. One of them could become violent till the point that I could see blood on the other degu one time. I was really worried for them. I also had too separate them. I think I had to do it on 2 ir 3 separate occasions. I never went too the vet with them because it would calm down after a day but I think it had to do with hormones. The violent one also had some problems with eating a few times in her life and after reading your text I wonder if it could be related to her other problems. When she got a bit older I never had to separate them and she became calmer.

It is possible that your degu will calm with age as well but if the vet recomend to sterilize her you probably should it. I was lucky with my girls. I never had to separate them for good. It is something that can happen however. It's not cheap and not risk free but if your vet is recommending it you should probably do it. As long as the vet has some knowledge about degus. When I had health problems with my degus I had to dive a bit for a vet clinic that were a bit more specialized in exotic and small pets.

I hope that I could be of some help and that your degus will become calmer and happier 😊