She's not angry..she actually is protecting you. If she doesn't do it away from the home, it is a protecting the home deal. That doesn't mean it is okay. It does need to be trained out of her. Until it is trained out of her, you may want to have her in a separate room or hold her as your guests get up. Just imagine how overpowering a tall human standing up must appear to a small Yorkie close to the ground.
There are ways to train Anna so that she doesn't think she has to protect you or the home...that you've "got this." I am the last person to try to give advice as I have a male dog (not a biter, but a big time barker) who does this protecting at home thing. I am the one at fault as I haven't put in the time and effort to properly re-train his brain and behavior.
I will hope some that are good at this, like Jeanie for one), will see this and give you some advice. When they do, take note and try it because these ladies that understand behaviors and training know what they are talking about.
Basically, I'm telling you that your Anna isn't aggressive, she is possessive and protective. It's a big difference. (My vet told me this). It is up to YOU to re-train her brain and behavior. And again..until that is done...I would keep her out of the situation of being able to bite..hold her or separate her from the room.
ETA: "these ladies AND gents" (per the post before mine
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