...My Fiancé's Friend Came to Train with Me ...

I'm in an open relationship with my fiancé, Alex. We both agreed that we're okay with each other dating and being intimate with others. A few weeks ago, Alex introduced me to his friend, Jamie, who happens to be a girl and has been single for some time now. They clicked right away... I felt happy for them. Later, Jamie decided she wanted to start working out more seriously, so she asked if she could train with me at the gym... It was awkward at first because there's an unspoken thing between us that neither of us wants to talk about, but can't ignore. We're both attracted to each other... It's not fair to Alex or Jamie to act on it, though. During a particularly intense session, I found myself looking at her more and noticing little things like the sweat forming on her skin... We had this moment where our eyes locked, and there was an undeniable chemistry... But then she'd break eye contact and focus back on the workout, as if snapping out of whatever we were in that instant. It's hard to keep it professional when my mind keeps wandering to what could happen if I let down these walls... Still, every time she leaves after training, there's this sense of missing out on something great, but also relief at knowing boundaries are respected... ...