What you are claiming here is that your ex girlfriend breached her fiduciary duty as the trustee of your account.  You are going to have to prove that what she did  - or didn't do I guess by stopping you from withdrawing funds - was in fact a breach under the law.  Go and speak with an attorney in your rea and bring with you all the statements and other evidence that you may have and see if it supports your claim.  Good luck.