She could if the guest became belligerent and advanced against her when questioned or ordered to leave. In the home, the legal and factual presumptions tilt heavily in favor of the homeowner and family occupants. Indeed, the point of Florida’s Stand Your Ground Law was to reinforce those presumptions and to make them applicable outside the home to those who are in the right.
Let’s put it like this.
While I am not fully knowable of such laws in each state, I would, regardless of your state, strongly advise you not to shoot guests who have been invited into your home by you, or another member of the household.