I sent a letter of withdrawal to USCIS on June 3 for i-485, i-765, n i-131. We have legal separation hearing Aug 16. We have not have greencard interview yet. However, you just stated the AOS will be valid until she leaves. Are both things correct?
It sounds like you're misunderstanding. If there has not been an I-485 interview, and LPR status has not been granted, the obligation under the Affidavit of Support has not yet started.
The Affidavit of Support terminates upon the death of the sponsor. But the sponsor's estate can still be liable for support owed prior to their death. ~Greg
