My husband’s step sister closely resembles his affair partner and I am get triggered being around her especially when we are swimming. His mom married his stepdad when he was 18 and he has 3 daughters. there is a 5 year difference between him and his stepsister that is triggering me so back then they didn’t really have much interaction but the last couple years we’ve gotten closer to her and his other 2 stepsisters. This particular step sister is the only one he has made an effort to talk to and hang out with outside family functions. She doesn’t know about the affair or that she is triggering me. He said he will tell her about the affair and that she is triggering me but I’m concerned he wants to tell her so she will have sympathy and reach out to check on him more. They do text occasionally now and I have told him that makes me uncomfortable but he says I shouldn’t be worried. His affair started with a childhood friend texting him to see how he’s been so I think he’s at a high risk for falling back into another one with her and I fear he is subconsciously wanting his AP through her because she looks and acts like her. My question is if he tells her about the affair should he tell her that I am getting triggered by her? I don’t want to feel like I am the problem. I am carrying a lot of guilt that this is an issue for me But I don’t feel safe.