I'd suggest she goes to one of the summer tours of her new school. It really helps with anxiety of the situation overall. Its pretty impossible to tell her everything she'll learn- but agree looking at the summer math packet will help.

Yes. We always looked at the summer math packet for the upcoming year during the summer. A great preview of the year to come. And gave the kids a few concepts from those packets to get their feet wet. Nothing onerous. A few problems a couple of times a week.

Pre algebra students take the Math 8 SOL at the end of the year. If you look at the summer math packets linked above (under secondary) then you will see the reviews for math 6,7,and 8.

Check out the summer review packets. They should give you an idea of the content:
https://www.apsva.us/curriculum/mathematics/

Fairfax has this: https://www.fcps.edu/academics/middle/mathematics/prealgebra#vdoe

which is good since I don't remember anything about algebra.

At least one teacher did not teach content much at all. I believe that teacher is gone but it’s a good idea to have someone review content with her weekly. Nothing is very hard. It’s just fast-paced. If the teacher is teaching and she’s doing the work, she should be fine.

We used Khan Academy together to review some content that wasn’t covered well in class. He explains things really well.

DD is excited about pre-algebra placement but nervous about middle school. She wants to see what is being taught so she has less to stress about. It helps with her anxiety. Same for social studies.

DD is oldest so we don't know anything about middle school curriculum. And the APS website didn't answer my questions: https://www.apsva.us/curriculum/mathematics/

I want to help her get comfortable. She wants to know what she will be learning in pre-algebra and try to get ahead. Maybe something on line. Maybe a tutor. (She wants, we are not pushing)

Any suggestions?