Hopefully the electric company will be reasonable. Hopefully, also, the original account application from 7 years ago has her signature. Hard to prove identity theft if she signed the account. When she moved out she should have taken the account our of her name. You should want the account to be in your name because if there were issues on the account in her name the electric company would not readily talk to you. You should just prove your residence with some other mechanism such as lease / rental / mortgage agreement. The alert is just their internal way of telling other operators ther eis an issue on the account. The electric company is in no way a criminal investigation.
Up to you whether you want to call various investigation organizations such as the attorney general's office, the FBI, local police and ask questions such as "Hey, are you looking for me for any reason such as, just hypothetcially you understand, identity theft?" Personally I wouldn't do it.
Other than transfer the electric account into your own name I wouldn't do anything. What will happen to her? Probably nothing, except she has broken her trust with you, the electric company, the school, possible her child.
If you do not suffer any actual damage then I would just leave this alone.
"And the old saying is, even when a lawyer represents himself he has a fool for a client." Lopez v. Johnson, 175 F.3d 1120, 1122 (9th Cir. 1999); Abraham Linoln is supposed to have said during his career as an Illinois lawyer "if a laywer defends himself he has a fool for a client."
You can miss defenses and say the wrong things if you are not represented by an advocate as your attorney.
Still, it is not recommended to try and defend yourself.
Check with a lawyer in your locale to discuss more of the details.
Good luck to you.
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