Big hugs to you! I think verbal stims are some of the hardest to deal with because they are so hard to ignore. I have a 14 yr old DS with vocal stims and I totally get how draining that can be. He's been doing it noticeably since age 3! That is 11 years of listening to near constant talking, humming, animal sounds, whistling, clicking, and hundreds of other random sounds plus accents and impersonation voices. It makes me nearly lose my mind sometimes!
As I understand it, babies and toddlers naturally stim for feedback but once they've squeezed what learning they need from it, they move on. An older kid who stims is sort of "stuck" in this toddler mode because their brain, for whatever reason, is not adequately receiving that feedback. Its like their brain never gets the "ah-ha" moment and just keeps driving them to explore the sensation. I get that, but he must also learn to live with others and not drive them to total insanity with constant noise either! So I tell him to stop if I need to. If he can't, I ask him to go upstairs or in another room for a while. I can't do this all the time or he'd never be near me, but during times when the noise is just too much or I am trying to talk to DH or something, I will expect him to show some control or leave the room. Perhaps this is something you can practice with her, depending of course on age.
As far as helping give her that feedback, I would suggest headphones with music, or maybe a keyboard with headphones. See if the feedback she is striving for is auditory. For DS it is. He loves any toy that makes noise. Battery operated baby toys have been banned from this house since forever since he will push the buttons over and over and over (yes even at 14!) and then repeat the little phrase throughout the day as well. BUT a keyboard with headphones give him the same feedback and keeps my sanity. And the bonus is that he is good at music. He has taught himself several songs and music is infinitely easier for me to listen to than clicking or mindless chatter!