I got caught by my ex mother-in-law (part 1)

I started going out with my ex-girlfriend Karla a few years ago and a few months later I introduced her to my family. Karla is a beautiful girl and super hot in bed, she likes to try everything without hesitation. We're both 20 years old and although we attend different schools, we see each other every day and almost every day we get together. I can say that Karla is the girlfriend with whom I have experienced the most things and one with whom I have lasted the longest. She's also the first one with whom I have a good relationship with her parents and they let me enter their house and even stay over occasionally. My in-laws treated me very well from the start and I won't deny that my mother-in-law Mariana gave me the impression that she sometimes flirted with me. She's a young woman, not yet 40, although she doesn't dress especially sexy, you can notice her tasty body through everything she wears. She works as an executive saleswoman at a bank and I love seeing my mother-in-law when she's wearing her uniform. A few months ago I had to open an account to get a new debit card and I asked her when I could come over for her to open it. She asked for my phone number so we could agree on the details. I went a few days later to open the account and Mariana told me that if I waited, she would take me home during her lunch break. That day nothing extraordinary happened but we talked about everything except my relationship with Karla. A few days later she called me to say that if I wanted to accompany her to go to Walmart for groceries since my father-in-law was going to be late and she would pass by the house on her way back. That was the first time I really saw that I didn't displease Mariana, not exactly as Karla's boyfriend. Mariana told me she had some problems with her husband and sometimes felt very lonely and between some comments said she sometimes envied Karla. At some point we took each other's hands to console her and she didn't let go. A few minutes later I looked for a kiss on the mouth and she responded, but when we left... He told me to stop, we got into my car, arranged the bags, and when we got in the car he gave me another kiss that came from her and she said if she knew it wouldn't hurt Karla she wouldn't hesitate to try something more with me. Of course, my response was that Karla didn't have to know and we could be very discreet, Mariana told me to come over to hers at 7 pm when she got out of work and we'd talk about it. That was a big yes for me or otherwise I wouldn't have wanted to see her alone again...