You did the right thing by writing this email. I can imagine how difficult it has been for you to know of this and feeling like you are carrying the burden of your family. I am going to be recommending you find the courage to take action, but first I want to offer a perspective supporting why I am recommending it.
Your mother’s secretly videotaping and then broadcasting videos of you and your sister without your consent would be enough for you to take some direct action. More than this she is being careless with her indiscretions, lying to you about her behavior, and disrespecting your father. All of these unfortunate behaviors are ticking time-bombs that will detonate sooner or later. You cannot control what your mother does, but you can make decisions for yourself.
The fact that you are out of the house but your sister isn’t makes matters particularly difficult. While you didn’t say your sister’s age her being home makes this challenging for both of you — particularly if she is younger. Your mother has consciously or unconsciously, put you both in a very arduous position. Her lack of concern for your wellbeing, your sister’s, and your father puts each of you in jeopardy. Her reckless behavior puts everyone at risk.
If the affair goes undetected (very unlikely in my experience) and you don’t take action it will leave you and your sister having held a dark secret. You already don’t respect your mother and are disappointed in her behavior. Whether she stops or continues there would be no reason for you to change this opinion of her going forward. It would be natural for a child to resent her mother for putting her in this position.
It also (by default) means that you would be keeping this secret from your father — and in a way betraying him. He is going through life thinking he has a faithful wife and a family friend, but instead four of the closest people to him are holding secrets. It is unfair of your mother to have put you and your sister in a position where you would have to maintain this secret.
If (I think when is more likely) the affair is found out you would have to cope with your father’s reaction. He may forgive you both for not saying something about it, but he may also be disappointed. Again, not a good position for you and your sister to be in.
In light of the negative consequences for staying silent the other option is doing something about it. But this will require you and your sister to get some support from outside the family, as you have begun with this email. I will encourage you and your sister to find a safe person to talk to about what is happening. Perhaps a member of the clergy, a trusted teacher, a school counselor, or a therapist. Finding some support as you get ready to deal with this is essential. Your sister and you are natural supports for one another, but having someone you both trust to hear your concerns is essential. You already are feeling alone with this and having someone you can trust to help you is one very important way you and your sister can take care of yourselves. Your mother denying the consequences of her behavior has created an emotionally abusive situation for you. Someone else needs to know about the difficulty she has put you in. Once you have the support you and your sister and this support person can consider your options. None of them are easy choices, but your mom has created an untenable situation that will require you to do what you feel is the best course of self-care for both of you. This could include confronting your mother by saying if she doesn’t talk to your father you will have to, talking to your father, having a therapist of clergy member as a support person who talks to one or both of your parents, or any number of other possibilities that would keep you from having to hold on to this secret.
You have taken the very courageous and important step in not holding onto this secret by writing us here. It is now time to take the next step by finding a person you and your sister can talk to about planning what comes next.
Wishing you patience and peace,
Proof Positive Blog @ PsychCentral