You should find an experienced criminal defense attorney. Remember that many criminal cases aren't about what actually happened, it's what the state is likely to prove beyond a reasonable doubt.
The answers to these questions may be different depending on your individual circumstance and should not be considered as legal advice or the establishment of an attorney-client relationship.
Hire a good criminal defense attorney ASAP. Under the law, for physical injuries, you are responsible for aggravating/making worse a pre-existing condition under a doctrine called "eggshell skull plaintiff". Next time your kid is bullied--don't take this course of action. First, get the written school policy on bullying and file a complaint with the school--they are obligated to investigate, but if their investigation does not turn up anything actionable in their opinion, they are not obligated to act. Then, every time your kid is threatened call the cops. You also get a local lawyer to send this woman a cease and desist letter. You've let it go too far, and now she has the upper hand, which makes the hiring of the criminal defense attorney necessary--or you can go through the public defender if finances are a concern. Her actions towards your kid will not excuse violence under the law.
We do not have an attorney-client relationship. I am not your lawyer. The statements I have made do not constitute legal advice. Any statements I have made are based upon the very limited facts you have presented, and under the premise that you will consult with a local attorney. This is not an attempt to solicit business. This disclaimer is in addition to any disclaimers that this website has made. I am only licensed in California.
You need a criminal attorney as soon as possible, especially in light of the escalating charges. Considering that 7, a criminal record could very well affect how and if you can be involved in your child's school and after school activities, a criminal lawyer will be necessary. If there are any witnesses that would be willing to come forward and give a statement on your behalf, that will also be helpful. You can go to the WSBA.org website and in the Lawyer Directory, do a search under area of practice and location for a list of criminal defense attorneys. Look up each of them to make sure that they do defense work and that they have not been disciplined. Good luck to you.