Thanks for sharing and reaching out to your community of stepmoms. We are here for you. Please know that you are not alone in this situation.
Personally, I go through something very similar with my SD10. While she does not visit with her mom (I’m a custodial stepmom) she does talk with her occasionally. Every time my SD speaks with her mom or hears her voice on voicemail (often my SD refuses to pick up the phone and talk - she is very angry w/ her mom for leaving) her demeanor towards me changes. It’s like clockwork which sounds like your situation. She gets frustrated, angry and disrespectful towards me.
You may be experiencing “transference” by your stepdaughter. Transference is a term used to describe when a person transfers feelings they have for one person onto another based on similar roles. For instance, my stepdaughter takes her anger, frustration that she feels for her own mother out on me - the mom in the house. It’s not me personally but the role I play in her life. She has even admitted to me that she loves me and knows I take good care of her but she often doesn’t understand why her mom isn’t here doing these things for her and it makes her angry/sad.
I get that. Still hard to take when you are in the middle of it. Know that it is not personal. I think it is great that you can see a pattern and it will be important for you and your stepdaughter to give each other grace during the transitional periods.
Thanks again for sharing. Never forget that your heart is in the right place and you are a great mom and stepmom. Stay strong and press on. Please stay in touch.
xoxo Heather