Not been my experience that a single fish by herself was shy and insecure. In fact, both fish I had (both were female) tended to be the more outgoing personalities in the tank at the time, coming to the front when seeing you there (looking for a meal handout, LOL). At least after a while, maybe at first they were more docile but in time they really came around.
I'm not 100% sure these fish died from being eggbound. What I can tell you though is they died in the exact same manner and it was quite sudden and unexpected. They were looking fine, with no reason to expect anything amiss, to within a couple hours of their death. The last few hours were spent bloated, difficulty swimming. The bloat part is clearly indicative of something - but whether it means eggbound, digestive/intestinal, or perhaps some kind of aggressive parasitic or microbial infection, is something I don't have enough knowledge to truly identify. Just very weird to me though, that both fish, and this happened years apart, died in the exact same manner.
It could just be spectacular coincidence.