If your child goes to public school in the US, you are likely entitled to the school testing her through one of their diagnosticians. Unless you think she is twice exceptional where the testing may need the nuanced experience of a private professional, I'd talk to the special ed director at your school and request the screening. If they push back, you can submit a request in writing. This starts a legal ticking clock where they have to respond to your request within a specific time frame.
We have used both school and private testing, and there are advantages and disadvantages to both. So I'd start out with free and then work from there depending on the results.
