Being co-executors means you both have the power to act for the estate; it does not mean that every action needs to be ratified or confirmed jointly by two of you. So it is legal for her  close out the estate without you. That said, if she failed to followed to the terms of the will, or benefitted herself at the expense of the other beneficiaries (e.g. paid extra money to herself), or was negligent (unreasonaby careless) in how she managed the estate, she would have violated her "fiduciary duty" and so acted illegally in that regard. If you think something like this may have happened, you can bring, as co-executor, an action (i.e. a lawsuit)  "for an accounting" to hold her accountable for her actions. It would be best to retain an attorney to help with an action like this.