I work with a few different kids with extreme anxiety issues, and it seems like each one has a very particular way of working through it. It varies a lot from child to child, so I'll list some things that have worked for me with differnt children.
-One girl I know can work out of some situations with humor. So for example, she might ask me a question that she already knows the answer to, just for the reassurance. If I always answer the question, this will never go away, so to wean her off it of I make up a silly answer. The first few times it really caught her by surprise, but then she got to the point where she could joke along with it. Now she doesn't ask anymore.
"Where are the kids in the other class?" she always asks
I used to say
"In their classroom, 240." the answer
then I switched to
"I ate them" or "In my shoe"
and she'd laugh and say
"NO! in their classroom!"
and now she doesn't ask anymore.
humor works better for things on the lower level of anxiety..... not very high stress situations, of course.
- the same girl in very high stress situations needs to NOT be talked to in the moment. "Get a tissue, take a break in the break area." If I engage her at all in the thing she is worried about, she will melt down for at least an hour. If I am very matter of fact, she works out of it within a few minutes and we can talk about it at a MUCH later time.
- another girl I work with cannot be left alone in high-stress time, her anxiety needs to be very carefully worked through with talking. She needs empathy, she needs to hear that I have felt those feelings before too, and I have found a way to work past them. It usually takes a 15-20 minute conversation to get her out of her anxiety.
- that same girl now uses a "worry box." I helped her decorate a box with stickers and pictures, and put a pink marker and index cards next to it. She can go to it whenever she wants to (she usually does about once an hour when things get overwhelming) and write her worry down and I check them twice a day and write a response. She keeps the cards in the box so she can use them whenever she needs them.
---- So in your case, I would just keep experimenting to see what kind of routine of talking/not talking/something else works. It sounds like it's not an explosive anxiety, but something that keeps her throughts occupied and stresses her out. I find kids with anxiety REALLY like a routine to come out of it, whatever the routine may be. Sometimes it's a mantra: "Mommy loves you. I always love you. I will not be mad at you. What do you want to tell me?" said in the SAME way every time. THEN after she tells you, follow it up with the same language. "See? I told you Mommy loves you, I always love you, and I am not made at you." so that the next time when she hears those words she remembers that last time you worked through it and said it after.
One thing I've noticed about kids with anxiety is that they don't recognize that their feelings WILL change in the future. They think if they are sad/worried/etc now, they will ALWAYS be. So I've also done some bets in the moment:
"I am UPSET and i will ALWAYS be UPSEEEEEEET!!!"
"yes, i will NEVER Be happy again!"
"wanna make a bet?"
"if I see you smile within the next 2 hours, then I am the princess for the rest of the day. If you are not happy for the next 2 hours, you are princess for the day."
sounds silly, but it works b/c each time we do it, she remembers that "ohhh yea, i didn't win last time... maybe i will be happy soon."
point being, you do what you have to do, you get creative, and very different things will work for different kids.