Note that I am not licensed to practice in your state. This is not intended as legal advice. Please check with an attorney in your state.
You need to immediately file a police report and tell them this is identity theft and fraud and give them all information regarding the ex. Even if they don't find her, you will need the police report to clear up the situation.
Take the police report and file a identity theft investigation with all 3 credit bureaus and every credit card that was involved. This will take time and a lot of work but eventually, they will clear your name of this situation.