For the moment, I wouldn't allow her loose in the house or out in the yard with others without a muzzle on. For meals or times when you want to let her have time to chew on something, I'd confine her until she's done. That should keep everyone safe, until you work through this.
As long as she checks out as healthy, I wouldn't focus on her age too much. I would handle her the way you would any dog of any age with these problems.
I wonder if she's getting a clear message from you that you find her aggressive behavior unacceptable or if she thinks you're maybe not that happy about it, but basically okay with it. I know you have to deal with the immediate chaos at the time of the incident, but are you also correcting her? Is there any consequence to her behaviors?
Do you think she thinks she's in charge and can do as she wishes? Is she submissive to you? Do you do regular obedience work with her? Does she obey commands well for you?
Elderly dogs can get a little more crotchety or a little more independent in their last few years. In our house, a couple of years before they pass, they can get a bit of a Diva thing going. Sometimes, too, we love them so dearly, see the end of their life getting just a bit closer and have a harder time being firm with them. I don't always keep up as much with obedience work as they get older, either. I'm wondering if any of these things could have let an underlying issue flair up into a more extreme problem.
Maybe think about it and think about whether you want to try to work with her for a little while. I think using a muzzle on her might buy you some time and peace to think. You might want to think about keeping her on a leash, so you can physically control her. I'd also do obedience work with her. You could check out some of the NILIF information that's out there and some of the sites on aggression. Some of that might ring true for you, when you read it.
In the end, only you can make the decision on how you want to handle this. I don't think anything you decide is wrong. Keep your animals safe while you give yourself time to work through this decision and just do what you think is best.