Learn English – Who is the subject(doer)? (There, she’s said it)

There, she’s said it.

1- Could you tell me please who the subject(doer) in a sentence like above is?

• The last subject or questioner(in this case David)?
• The others(all the peoples who are present there)?
• The subject is uncertain?

2- What does refer it to?

3- What's the meaning of there here?

The full text is:

It seems to me,” Henry says, in his slightly pompous way, “that if
this is a murder, it would be almost impossible to solve. It seems to
have happened in the middle of the night. We were all asleep in our
beds. There are no witnesses. Unless someone wants to confess, or
share some helpful information about seeing someone creeping about in
the night, I don’t see that there’s much to go on.” Beverly listens to
him, licks her lips nervously, and waits. No one else volunteers
anything. Finally, she blurts out, “There’s something I should
probably say.” All eyes turn her way. She almost loses courage. She
doesn’t know if the argument between Dana and Matthew is relevant or
not, but it will certainly sound damning. “What is it?” David says
calmly, as she hesitates. “I heard them arguing, last night.” “Dana
and Matthew?” David says, as if in surprise. “Yes.” “What was the
argument about, do you know?” She shakes her head. “I heard them
shouting, but I couldn’t make out any words. Their room is next to
ours, on the same side of the hall.” She looks at her husband. “Henry
slept through it all.” “What time was this?” “I don’t know, but late.”
“Did it sound . . . violent?” David asks. “I don’t know. It was just
raised voices. No crying or anything. Nothing slamming, if that’s what
you mean.” There, she’s said it. If Matthew’s done something wrong,
then it’s good that she’s told them.