You present a novel question. Unless there was a court order prohibiting you from deleting information from her account, there is no basis to punish you in this regard. For example, temporary orders are issued in a divorce prohibiting the parties from selling assets or changing insurance information, etc.
The other issue is that technically this was a marital account, since it was established during the marriage and you both used it and had access to it. At worst you may get a slap on the wrist and stern warning by the judge if she takes this to court. It would be interesting to see an issue like this go to court because the argument could be made, successfully I think, that it is marital property and until the court awarded the account to your soon to be ex, either party still had the right to access the account in whatever manner they chose. Furthermore, she should have changed the password XXXXX she did not want you to have future access to the account.
Obviously, you should not engage in this type of behavior again but unless it was real property or financial property I do not think there is much recourse that she will be able to pursue against you especially with the history of the account as being joint at one point and being accessed by you throughout the relationship with her knowledge. I hope this helps clarify.
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