Need Advice

Hi. So I’m needing some help with the situation I’m in. I’ve been married to my military husband for over 4 years. He has this girl best friend who he had sex with and was in love with before we got together. She’s staying with us at the moment to visit. Recently, I just found out that they were sexting each other while he was away for training and that absolutely killed me. My husband never told me that he was unhappy in our relationship. I hate her for what she did and never coming to me to tell me what they did and just being fake to me to try to be my friend. My husband and I are trying to work on ourselves and our relationship, but it is so hard for me when she’s here. I want him to remain her friend since it’s important to him but it doesn’t feel like our marriage isn’t as or more important. I want to fix us. But it just feels like everything is falling apart. We have two kids together and if we were over, I’d have nowhere to go. Please help.