I think the best thing to help her-because I have a friend who is strongly on the AuDHD spectrum and is helped a lot by his incredible girlfriend, is converse with her in a series of questions that creates external structure.

Not everyone's brain is the same of course, but the communication issue is that her brain is running faster than her memory can keep track of and her mouth hole can finish thoughts coherently. The information is there, its always been there, she struggles to parse it in a neurotypical way. What you have to do is take away the ADHD "decision matrix hell" that our brains get trapped inside and create a single track with limited offshoots so we do not get immediately overwhelmed and derailed.

Try sitting her down and simply ask a series of questions about whatever topic at hand. Who? What? Where? Why? Don't ask how because that can trigger a tornado of thought train processes. But get her to work inside of a structure that's simple. Each of those questions should boil down to an answer less than 10 words for most things. It might help to start this on paper too, leave her one to two lines for each statement.

This could help in professional communication too if she can start to practice answering everything in the four-W format, it will be a lot easier to keep things clear.