I doubt she knew that severing caused you to be released from the Oaths. Otherwise, forget the Healing, she would simply have waited till she could be sure Egwene could link with some women, told them she was Black Ajah, had them still her, and then spilled all. This way, she ends up alive with a future chance for Healing.

Based on Verin's work with Irgaine, Sashalle and Ronaille, I don't think she knew they were Oath free. She did ask to meet with them, and nothing suggests she figured out their Oaths were no longer valid.