Is a wife's recounting to her mother, aunt, or friend about the injustice she suffered from her in-laws, for the purpose of venting or seeking advice, considered backbiting, knowing that she mentions real events that happened to her?

Complaining about an oppressor is permissible according to Islamic law, based on the Almighty's saying: "Allah does not like the public mention of evil except by one who has been wronged." Therefore, if you are truly wronged, there is no sin upon you for speaking ill of your oppressor in the context of seeking redress. However, if you are not certain that you have been wronged, then it is not permissible for you to speak ill of anyone, as that would be forbidden backbiting. It is permissible for you to seek advice and consultation by mentioning the act without explicitly naming individuals.